Several members including cantom, stoggie and I have been on this trail for a while
First off, you'll have to figure out if it's an Mk1, 2, or 3. Once that has been done, you can start sourcing parts. Specifically, you'll want to mesure barrel length. If it's the MKIII/M10 military rifle and the barrel measures under 30 1/2 inches (I think, I can't remember if that's muzzle to front or rear of reciever ring) then the barrel has been cut down and you won't be able to reasonably restore it. (***** It could also be a factory sporter, if it is, don't mess with it, they're rather valuable. Also, some WW1 snipers did cut down their ross M10's on their own.... it's a case by case evaluation on that.)
Anyways, if it is a former milsurp that has been sporterized, and has a full length barrel.... good luck
Firstly, there is one CGN'er who has recently begun making repro stocks. Before that, there was one guy in virginia that basically had to be harassed to make one stock. If a repro stock is unavailable from the cgn'er here, then you'll have to get a stock that has been cut forward of the rear band, so that you can splice a matching piece of wood underneath the rear band to make the stock appear original. So far I've done that once and it takes some time.
Next you need at minimum, the nose cap. Stamped MK2 nose caps are slightly more common than the milled MK3 nose caps, but only by a little. MK3 nose caps are prohibitive to have made as reproductions, as the way they were made and the cuts involved are not strait forward for machinists. I've tried to go that route, and it's darn expensive
Anyways, that's probably the start. You may need more screws, sight hood, rear sight, butt plate, etc etc etc etc. Post pics when you see it and people will be able to offer better advice.