If the problem you are trying to fix is the appearance of the carpet, why not take it back to Circuit City and have them fix it to your satisfaction?
In my city, both Best Buy and Circuit City do crap installs on just about anything. Only thing I'd trust them with is sliding in a new radio and harness - if they didn't have to do any disassembly of the dash.
People frequently complain about things like you've described as well as scratches, broken pieces, etc. The store usually responds, when pressured.
I'd go back, ask to see the store manager, and politely - but firmly - explain the problem. It would help if you explain what you expect to be done to rectify the situation.
I've seem people get their problems fixed, and often a refund of some/all of the installation charges.
You take a risk when you let one of these chains work on your car. I've heard of some good, but mostly bad.
They are, however, big companies that have a chain of command you can follow to get satisfaction. Key is to be calm, polite, and firm.