ACL Surgery Opinions - has anyone had this done on their cat?

My cat is scheduled for ACL surgery in a few weeks.  Everything i've read indicated that it's a good idea. 

i go back and forth on having the surgery or not

the cat hasn't been eating and he went on an appetite stimulant and that worked, but now he has his diarrhea again.  Not sure if that's because I opened a new bag of nv limited ingredient dry food. 

i don't think his appetite problems are because he is in pain from his knee, but who knows.

i'm afraid of him having surgery, then not eating. 

I haven't known any cats who've had this, but I have known a few dogs and humans. They've all been better off after the surgery. It's hard to keep them still and off the leg post surgery, and I imagine it will be the same for your cat.
It's possible the pain is putting him off eating, making him feel generally unwell. I guess you won't know until afterward, unless you find out something else wrong beforehand. Will he be getting pre-op bloodwork?

yes on the pre-op blood work

not sure on the eating, it's very perplexing

he absolutely fits out at the vets, he's a very loving guy, but anxious, can't let anything go

i honestly can't stand the thought of putting him through so much pain