I am thinking about getting a sugar glider as a pet. What are the main issues I should think about before getting one? Also, I am planning to buy a dog (boxer) later on when we move to a bigger home, will the sugar glider and dogs get along?
I'm inclined to say that dogs and sugar gliders are not compatible together, because there are enough cases where even well behaved dogs have killed sugar gliders. Even if it's accidental, I don't think the risk is worth it.
The simple fact of the matter is that sugar gliders are tiny compared to even small dogs; and are so delicate that even though the dog might mean well, an accidental step or a playful nip can cause serious damage.
Another thing to consider, is that sugar gliders have not been tamed on nearly the same level as dogs, they will still react heavily on instinct. If they feel nervous around the dog, which is pretty likely I say, their defensive instincts could kick in and they might lash out at the dog.
That's not to say you can't have both animals in the same house, just that you won't really want them interacting with each other; at most only under strict supervision.
You'll want to set up a wire cage for them to keep them contained, but you'll want to make sure it's large enough for them to get enough exercise while inside. Sugar gliders are nocturnal, and it's not really a good idea to let them wander around unsupervised at night. A minimum size for a pair I would say is 24x24x36-inches, and make sure that you have a way of latching the door shut that they can't figure out how to undo.
Of course since they're nocturnal, that means you also have to take into account that you won't be seeing much of them during the day, and you'll need to work around their schedule as they're very social animals and will require lots of attention. You don't have to become nocturnal yourself, but definitely devote the evenings and early mornings to caring for them.
You'll probably find differing opinions on what to feed them, since they're still fairly new to the pet industry, their needs haven't been documented as well as the more common pets. What I can tell you is that sugar gliders are omnivorous, so they will need a combination of fruits, vegetables, and insects in order to be healthy. It's also important to provide them with a calcium supplement to prevent metabolic bone disease.
I would review this list for foods that you can feed sugar gliders, though I'd ignore bananas and any citrus on the list as most sugar gliders don't seem to like those foods. Other foods you can include are crickets, mealworms, and small amounts of unprocessed, boneless, lean meat.
There are also varying recipes for mash you can feed them. Commonly using ingredients like egg, applesauce, and yogurt.
You will want to vary their diet so that they don't lose interest in eating.
You will need to glider-proof your home if you plan on letting them out of their cage. Toilets are notorious death traps for sugar gliders, as their curiosity leads them in and they're unable to climb out. Even putting the lid down isn't enough as sugar gliders can fit into very small spaces.
Other places to consider are cabinets, if there's access into the walls from underneath sinks, the kitchen appliances, make sure the outlets are safe, the laundry room if you have one, and any air ducts in the house.
Here is a link to a more detailed list, and she discusses her concerns about keeping sugar gliders with other pets.
Sugar gliders are very high maintenance pets. They require an enormous amount of attention and care, and they are very fickle little things.
Do not get a single glider - they have a huge amount of trouble living alone. Get two or more, or don't get any.
Your house will need to be thoroughly prepared for sugar gliders. They can fit in tiny spaces, climb on everything, and glide to the last places you'd imagine.
They chew wires, pee and poop everywhere, and knock stuff over left and right. Their diet requires live insects and grubs, and you'll probably end up with a bunch of renegade cricket escapees living in your house.
Their diet must be varied constantly, but any given glider will have its own tastes, and will reject foods it doesn't like. You need to have a constant supply of fruits, vegetables, and insects at all times, and you'll probably have to hand feed the gliders a significant portion of the time.
They are extremely grumpy during the daytime, and extremely active all night long. Expect to be the landing pad for endless glides. They will climb the highest object in the room, hop off, glide across the room, and land directly on top of you, while you are sleeping.
Most owners will make a sort of nesting bag out of fleece, and keep the gliders inside it while they are sleeping. With a drawstring, you can wear the bag around your neck. This is adorable and sweet, but it will quickly drive home the fact that gliders are absolutely unbearable during the daytime. If you so much as move the wrong way, they will grumble and grouse about it for several minutes. If you try to wake them, they will make you pay the price. They hate being woken up or disturbed while they are trying to sleep.
You need to find one of the very few veterinarians who actually know how to treat a sugar glider. Most vets have no idea how to handle tiny marsupials from Papua New Guinea. Expect to pay top dollar for medical care.
You will also have to shell out the bucks for nutritional supplements, because gliders are so finicky and stubborn about their food.
If and when a glider dies, you have to buy another one, because they die of loneliness. A solitary glider is a very unhappy glider, and will probably become a dead glider sooner than later.
There are also moral and ethical concerns regarding the owning of sugar gliders. They are not a very common species, and it is likely that a large portion of the gliders that end up in a pet shop have been trapped in the wild and shipped overseas. By purchasing a glider, you are making yourself complicit in the depopulation of wild gliders.
In short, you can't just ask people on this site what you need to consider before buying a glider. You need to buy some books on the subject and read them in their entirety. Bringing sugar gliders into your home is not a decision that should be taken lightly. You are considering making a decision that will require an enormous amount of time, money, effort, education, and lifestyle changes. An incredibly active nocturnal animal is a challenging pet to own, and gliders are even more demanding than most other animals.