Unless your cat is symptomatic, I would recommend having a dental done. FeLV means you have to be even more careful to protect your kitty's health, and mouth problems can be nasty if they're not taken care of quickly. If your cat's current health is good, he should have no problem handling gas anesthesia and it's far better for him to have that and get his teeth really clean, rather than put it off and risk serious infection setting in.
Given your cat's FeLV status, I would recommend consulting with a board-certified veterinary dentist and seeing what s/he recommends. I see that you are in Maryland and I can personally highly recommend Dr. Ira Luskin. His practice has two locations, in Annapolis and Baltimore. The website is http://www.animaldentalcenter.com/
. Dr. Luskin is considered to be one of the best in the country and I can personally say that he saved my cat Mikey's life.