A couple of thoughts...
"hasn't functioned properly"...can mean just about anything. Quite frankly, I don't see any reason why we couldn't help you fix yours and get it up and running properly. And do so for a tiny fraction the cost of a Springfield too. Could be $100 in parts...might be a $5 spring...or maybe just some elbow grease, but I'm certain yours is fixable without breaking your bank account.
BUT...for us to help diagnose the problem with your rifle, we need to know more about what it's actually doing. The more specific you can be, the better. And while you fix it yourself with our advice, you'll learn about it more and come to appreciate it.
Regarding the original title of this thread though, in all honesty, I think there ware plenty of options for adding to any M14, from original stocks, to target stocks, to nice wood stocks, aluminum military stocks for bolting all sorts of lasers and night vision... there are match iron sights, match spring guides, old style slings, marksmanship slings, bipods, probably 100 different options for mounting scopes...there are many options for springs and small parts, be it new mfg or USGI.