Another place to look (not already mentioned) would be Indy-Pen-Dance.
I will note that I have had various repairs done on various pens by pretty much everyone who has been suggested so far. But I've had Mike Kennedy of Indy-Pen-Dance do all my Vacs, after a friend's recommendation at my first pen show (one of the first "show" pens I ever bought was an Azure Blue Sub-Debutante; my friend (FPN member Uncle Red) had gotten some nib work done by Richard Binder, and Richard recommended Mike and Linda to him, and in turn the recommendation was passed along to me.
Ruth Morrisson aka inkstainedruth
ETA: I should say though, that I've generally had work done on pens at shows, not through sending them out. I can't say what sort of turn around time any of these people have if you're mailing them the pen. The advantage of shows (if you can get to one, of course) is that the people are right there -- you sign up on a waiting list but you can also talk directly to the repairer on the spot, and explain what the issues are, and if you need something like nib work you can then try the pen and say "No, not quite right yet" or "Yes! That's PERFECT!"
Edited by inkstainedruth, 09 October 2019 - 17:38.
"It's very nice, but frankly, when I signed that list for a P-51, what I had in mind was a fountain pen."