Your vet will be able to give you specific instructions for your situation, so please make sure you sit down with them and discuss any and all concerns you have about this surgery.
I've never had a cat who needed intestinal surgery, but we did have a cat who had a hiatal hernia repaired (his stomach was moving into his esophagus), and later he had a gastric feeding tube (the end was placed in his stomach, bypassing the esophagus, where most feline feeding tubes are placed), so I'm familiar with some types of gastric surgery.
The most important thing to remember about this surgery is that it is MAJOR SURGERY. Your cat will take time to recover.
If your cat is on pain medications, she will likely start to feel better before she is better, so she must be confined and not allowed to jump until the sutures heal. We kept our cat in a small bathroom, but he was not naturally a climber. If your cat would normally climb on the toilet, sink, etc, you should instead confine her in a large dog crate, room, or large closet without any furniture. Your vet will instruct you on how long the confinement should last.
I do not remember giving our cat special food after the surgery, but he had so many allergies that his food choices were already pretty limited. Your vet will give you a large number of medications to ensure that the GI system is working properly again, so make sure you administer them according to their schedule (we had to keep a calendar because it seemed like everything was on a different time table).
The good news is that if everything goes well, your cat should be back to normal in a few weeks. There is a risk of complications (as with any surgery, even something routine as a teeth cleaning), and your vet should discuss these risks with you.