The timing belt parts itself doesn't cost more, maybe around 60 to 80 bucks you can get a decent brand parts. It's the labor works that takes lot of time; usually manufacture and mechanic suggest you to change your vehicle timing belt for every certain miles but you can always do a quick inspection by looking at it.

My suggestion is: if you plan to sell it, do not fix anything. you would be better off finding a local mechanic to do it for you for couple of hundred bucks; the high end guys are rip off.