Congratulations. Now comes the bad news. Buying a correct period correct set of grips will cost you as much as the gun!
I have no idea what your level of experience or competence is. What I'd suggest is you do some soul searching and figure out if you're capable of a full tear down. Its not rocket science. I'd suggest a full interior cleaning and lubrication. It might not even need it. But a good quality oil or grease (your preference) will do a lot.
There are a number of solutions to the grip problem. The cheapest and a good one would be to just look around and find a set of postwar N frame target grips. If they fit your hand and your liking, go for it. If you want period correct service grips, be very careful to make sure they'll fit before you spend you money. If you want prewar Magna's, get ready to pay. $500 is a nice round figure for great condition ones. Its because you're competition with all the RM owners out and about. Another solution would be to contact Keith Brown and have him whip up a set of his reproductions. He's not cheap or fast, but he's really good.