thats good you had your billy in for a snip. Let us know how it went..
when i had both brownie and lady done the vet gave me medicine to take home for th pain.. make sure you get that too... you'll use a syringe and this liquid stuff. (forgot the name).
last year i had my bun mopsey fixed and never received any medicine for pain when i brought him home... he later did pass away a few months later... (rest in peace my little guy). THat was a different vet office i have since changed my vet and even wont bring my dog there, i bring him to the new vet place. well, anyways good luck!!