I have a Nikon 28mm 2.8ais that I need to get looked at. Bought it used and the focus is stiff. It'd be great to have it overhauled to make sure it's up to par.
I've used International Camera on some Pentax issues without problems, but found they were more expensive than actual Pentax specialists. I would find somebody who specializes in Nikon lenses and send it to them.