I second Bo's advice with a small tweak to it. I am also a first time dog owner. Kaji was already a year old when he came home. He was fully developed physically and personality wise. He did not change one bit after the surgery. He is still my cuddly love bug who has spazzy playful moments. If I ever get a second pup, I will wait to have him neutered until his growth plates closed and he has had a chance to lose all those baby teeth in their own. You can ask your vet if your baby's growth plates have closed.
Oh, and you must MUST look into the Kiss E soft collar. It is so much nicer than those plastic cones, and they're handy to have. I unfortunately bought mine after the fact. I've used it to keep Kaji from licking cuts.
__________________ Littlest JakJak 
We miss you Kaji  |