Just so you know, the only fully original M1 Garands I've seen, are a few Danish Breda's or rifles that were matched with original parts later. If your rifle is well used as you say, the repair facilities wouldn't worry to much about which manufacturers parts went into them if any needed to be replace.
Being an IHC, it would have been manufactured post WWII. IIRC. Maybe even saw Korean War service. It may also have been sold or lend leased to one of several other nations around the world. Maybe even given to the ARVN in Viet Nam.
Whatever you decide to do with it in the end, is up to you. There don't seem to be a lot of them coming into the country anymore so no matter what you do, it will retain much of its value. JP, told you the truth. You will never regain the cost of restoration. I have a hunch though that the Korean M1 rifles will be parted out, rather than be sold. It may take a year or two though.
Your rifle, is fine the way it is by the way. If it shoots well, that means the bedding hasn't compressed. It also means the replacement pieces were fitted properly. There is a lot more to refurbishing a Garand than first meets the eye. You may want to go to American Gunsmith Institute website and purchase a copy of their DVD on rebuilding the Garand. It won't be all you need but it will give you an idea of what you're up against.
Now, I don't condone changeing anything on a perfectly funcioning milsurp. The scars may be battle scars or maybe scars from training purposes or even from some previous owner that just threw it into the pick up, behind the seat as a cheap truck gun. I doubt the latter though, Garands have always commanded a premium.
From your pic, that stock looks to be a replacement or refinished already. Other than that, it looks good as is. If it has been refinished, just stain it to match the after market hand guards. Don't put any more money into it than you have to. Don't darken the gas cylinder either. That is their normal appearance.