My 4 year old yorkie is not neutered... I was considering letting him play stud at one point, but decided not to due seeing how many dogs needs to be rescued, and all the abandoned dog commercials..tears my heart

But anyway, my lil boy is my heart and I'm cringing at the thought of neutering him at this age. One because I dont know if at this age it's more painful for him or needs more recovery time, and two I'm so paranoid about leaving him at the vet especially possibly overnight. He still marks in the house, and I know this can still continue even with neutering him, but we have a spayed maltese who he terrorizes everytime they both go to the groomers for some reason. He comes back like a horny old man

and that lasts a day or two each time.
I apologize if this question has been asked before, I couldnt find it.