I don't personally know of a vet that doesn't use gas anesthesia on surgical procedures. Best gases are Isoflurane & Sevoflurane, as recovery is much quicker with these. A lot of vets, however, will induce anesthesia intravenously (the most common induction drugs are propofol & valium or ketamine & valium). This is actually the preferred way to go as then an endotracheal tube can be placed to maintain an open airway, which is especially beneficial if the animal crashes and needs to be breathed for manually. Also, an awake animal will find the anesthesia irritating to breath in so most animals will resist a mask being placed over their face.
Whether to neuter Percy wasn't an option for me as I have a bit of an aversion to dogs with testicles.
But I was a totally nervous wreck the days following the procedure. If you don't want to get him neutered though, that is perfectly fine and entirely your decision. But do remember that being worried is very normal and is due to the fact that he is your baby and not that neutering is an overly risky procedure.