$18 is a hell of a deal on a starter and should suit your needs just fine, assuming it fits based on what tranny it is made for.
Junkyards are cheap, but not cheaper than that. I have worked in a parts store for 2 years now, and your looking at something around $100 for one from Advance Auto. Judging by the situation, used is your friend. If you can get it off the car, any advance auto can test it on the alternator bench that they have set up in the back, that way you can see exaclty what it is/isn't doing.
Hope that helps some.