As far as the grips go, don't waste money on "authentic, original" grips. Any reproduction that suits your taste and budget will do. Brown wood, or black plastic are the period correct grips, so anything that looks like that should do.
If you know a highschooler taking woodshop, buy them a piece of walnut (or your choice) and a checkering tool and tell them to have at it.
(suggest they practice on cheap wood, first
)
I also suggest you get one of the Luger combination tools, and a reproduction holster (which holds the gun, the tool and a spare mag).
I have one of the repro holsters, and the only way you can tell it isn't original is that it lacks the correct German markings and isn't 70+ years old.
Check in your uncle's things (or with whomever has them), and see if maybe there isn't an "old holster", etc that went with the Luger...lots of times the executor will know about the gun (and other "big" stuff) but have no idea about the accessories that go with it, until it is pointed out to them. There might be a box of stuff somewhere that could wind up sold as junk simply because the people handling it don't know what it is.
Your gun is never going to be of interest to Luger collectors, which is not to say it has no value, it just has no collector premium value because of the mismatched parts and it being a fairly common model, so you won't "hurt" its value with a
quality refinish.
Sorry, but I can't help with that, no idea what a good job costs these days, but generally, if you buy cheap, you get cheap...
This is mine, a 1936 S/42 which I got about a decade ago. I was told it was reblued "by the factory, during the war" (you get told all kinds of things), and the grips while pretty, are not original. The price was $750, and I was told (again
) that if the finish had been original the price would have been $2200. (ten+ years ago...)
While there have been a couple of commercial attempts since (none surviving in the market very long) essentially Luger production ended in 1942. Yours is always going to have some value, because it is a Luger. Might as well finish it to suit your tastes.
Good Luck!