Bought used Oldsmobile yesterday, problems already

1992 Oldsmoblie Cutlass Ciera, a little over 91k miles

After looking around for a used car, we bought one from a dealer after test driving it yesterday. Looked great inside and out, sounded great, had low mileage and a pretty good price (we thought) at $2450. The salesman said there was no warranty, but that he would fix problems within a month if there were any. I noticed later that my husband signed a no warranty "as is" paper. So I know that we are pretty much out of luck as far as any legal action.

When we test drove it, it ran fine, sounded fine, everything seemed fine. Then when we drove it home, back out to the store, then back home again, we noticed when we were at a stop the car would make a noise, kind of like the sound of clearing your throat but low, not real loud. And when we got home, I noticed a smell coming from under the hood. We checked the oil and there was plenty of that in there. We didn't see any leaks or anything, but then again, we don't know too much about cars. I had him take the car back to the salesman to get him to look at it. The salesman said that it's probably the new brakes, and if it doesn't stop making the noise and smell within a couple of days to bring it back and he will look at it (and I guess fix it, or more likely say that we are out of luck). Well, today we noticed it is also vibrating the whole car, like riding on a bumpy road. Oh and on top if it all, the fuel gage fluctuates a lot.

Please tell me what to do! We don't have much money to fix it.