Yeah, they probably said OEM...
They put in an AC Delco part, on the invoice it reads "Air Mass Sensor", and when they told me what the problem was they simply referred to it as a "air flow sensor", which I assumed was the MAF, and when I read up on the diagnostic problems that a failing MAF causes, it sounded like it was what was wrong with my car... but now that I read up on the MAP I guess it really could have been either one. Since it runs now I guess I'd just have to look under the hood to check which part is new.
And once I actually read up on the problem and learned how easy it is to replace I would have rather done it myself, it's just that they had my car for a few days and I was so eager to get it back that I really didn't think about it until I had already told them to make the repair.
Either way, after checking the price for a Delco part on RockAuto.com I'm pretty sure I got taken for at least $120 on the part, more if they didn't even replace the core when the replaced the MAF (which is another $60 easy).
I probably won't ever take my car back there again, which is somewhat disappointing, since the seemed nice enough and even gave me a quick list of other things that would need to be repaired in the future... although now I'm just wondering if they weren't just baiting the hook to reel me in again.
I guess at this point I'm wondering if there's anything I can do to get some of my money back. Though I realize I should probably just let it slide, but I'm a grad student and could really use that extra $120 they took me for.