Sight components align with was was used on it as it came from factory? Op rod should be marked as well. Gas lock cylinder and screw? Stock is a big one, as correct stock with a good cartouche is desirable.
Some people really get into it, and fully matching will have more value depending on purchaser. Cmp gun with paper work will too (you can send them the serial and theyll do a look up for 25 bucks, but that might add value so consider it).
Most guns have non matching barrel, so I wouldnt worry about that so much, most were re-arsenaled post war either by us, or other armories (lend lease guns).
Generally speaking I would expect to pay 900 to 1400 for a Garand nowadays depending on what it is, condition, rarity, components, etc. E.g. winnies are usually on the higher end of that scale, as are clean examples of other makers. Beat up field grades on the lower end and under.
Either way, what you have is an awesome piece of history of which no more are being made, and so make sure you enjoy her, and also use proper ammo to keep her happy.