Oldsmobile/Buick Repair: Buick fuel usage, buick century, fuel usage

Question
I have a 1997 Buick Century. Last summer I was hit in the drivers side door, and it was replaced. Since that, the car uses twice as much gas as it had previously - the body shop says to take it to the dealer, which is gonna be $$$. The car runs ok. Someone told me to disconnect the battery for longer than 15 minutes to reset the computer... any truth to this? Thanks

Answer
I don't think so, but what have you got to loose? Just need to reset the clock.
If there were a code stored, then there would be a check engine light on.
I believe after about 95 you need a scan tool to read and erase codes, but a lot of parts houses will do that for nothing, in the hopes they can diagnose a problem and sell you some parts. Win Win situation.
Ypu cpuld look under the car and see if any wires were cut, or left disconnected, but I can't think of any reason a hit in the side would cause a diff in milage.

Van