We had awful eating and sleeping problems pre-op, in that she ate very very little. I know its tonsil related, because she used to be a good eater - and when well, a good sleeper. The last few months she's not been more than 3-4 hours without waking up, at the very most, often less.
She had severe sleep apnoea, and found eating hard work. Summer was better, some of the time, but since October (colds etc) its been pretty grim.
I'm thrilled with the results, everyone here told me it was the best thing they ever did, and I can see why. I really hope you get the same benefits!
Don't expect too much from the eating for at least a week post-op, I found offering tiny snacks often, in front of a DVD (she was too tired/sore to cope with sitting at table), worked best. I also gave her mini cornettos and apple juice ice-lollies during the swelling stage (first few days post-op) as well as offering toast and crisps and other 'rough' food, because they clearly soothed her, and hydrated her. The food she's wanted has changed according to the healing process - some days she hated milk and all dairy, I guess it tasted weird.
Good luck, hope it continues to go well!