As far as the shots on your girl, please watch them.. I usually always give benadryl before rabies shots… and also I never have any other shots given with rabies... Watch for a reaction and since she already was have a problem at the injection site, I really would watch it. I have seen Basenjis get really nasty sores at injection sites from Rabies... and you might want to just give her a Benadryl. Not sure that I would just automatically say she has allergies cause her eyes are red? However, it is surprising that the vet didn't seem to be concerned? I would be.. could be food related? Could be something in the house (being new)...
As far as Chance, he should not be too groggy after being neutered, depending of course on what they give him? Did you ask about the anesthesia they use?... but he will NOT want her around him.. and you need to make sure he has peace and quiet. And whatever you have to do... she needs to be "contained" By morning as Lisa says he should be pretty much OK.. if he tried to do too much, like jump on the couch, etc... most likely he will "sqeak..."