Naturally it does matter who you talk too, - replacing the stock will cost at least $200 if the stock set is worth having. Then you will have an ill fitting mismatched stock instead of a original cut down stock.
If your goal is to increase the value then buy a new stock set and keep your original stock, then you will do no harm, the baseline value will rise but odds are excellent you will not have improved your bottom line value. The cost of the stock you buy will not be recovered fully in the pursuit of a better rifle. (you will probably spend more than it will increase value)
Mismatched parts added to a rifle increase value to the degree the parts are of value, - the value of the sum of parts - when you go to sell such a rifle it is generally true you are better off splitting up a project rifle.
Anyway, I am not trying to dissuade you, but in my experience you can't fix sporterized rifles, sometimes you can make them better, but economically it is far cheaper to buy a rifle that you do not need to "fix". They cost more up-front but you can't change the nature of a rifles originality anymore than you can change a persons character.