....we need more information. Is it an autotragic? Not shifting? It doesn't seem unheard of to me for a motor to be spinning at 3900 RPM at 70. It's relatively high, but Honda's tend to be peaky, rev-happy motors.
Since the economy is failing, a lot of places will diagnose your CEL for free. NAPA and AAMCO, to name two. Go there, and get them to read the code. Write the trouble code that set the light off, and type it in google to see WTF it is.
Cobalts are a more modern design and by far better than the Cavalier. (That's still not saying much). Don't let the fact a car is manual turn you off from buying it....they aren't hard to learn and improve...everything.