ecm needed

[jza80king]

So I got a call from my mechanic and after having my car for 1 week almost 2, he is telling me that the ECM is malfunctioning. First off, my car is a 92 DOHC auto, how likely is it that the ECM is bad? I mean my car just runs like **** then all of a sudden it runs great. Its like a switch, it comes on then off. Anyway, my question is i'm seeing a bunch of ECM's on ebay within $50-$75 some say 'tested' or 'in good condition' and I was wondering if any of you have had any experience with ebay and buying ECM or anything similar? I'm gonna check out the classifieds here on the forums but I wanted to see what you all thought.