Good luck today (it is tomorrow your time already). I know everything will go fine. Hang in there.
Poppy will want lots of cuddles when she comes home. When I had my Poppy fixed, we laid on the floor together for three days and two nights (yes, I made a pallet out of blankets for us). I rented several movies and vegged out with her on the floor.
The pain meds the vet gave me had a mild sedative and helped to keep her from jumping around too much (this was nine years ago so not sure if they still do this).
In a few months watch out for my posts when I take my babies in. I will need you to remind me how smooth Poppy's surgery went