Here's a little info - hopefully some of it helps.
First off (too late, I know), Best Buy calibration and most Geek Squad things in general are horrible values. There are true audio/video professionals out there, and I can guarantee you the kids at the local Best Buy are almost never one of them. They have some training and equipment and that's about it. Also, don't buy any cables or equipment there. Monster cable is so overhyped and therefore overpriced. Go to monoprice.com and order your HDMI cables or other random accessories. HUGE difference.
As someone above mentioned, the AVS forums are a great place to look for information regarding your television. There is a neverending stream of knowledge there and it's an amazing community.
Back to the question at hand, there should be no reason to lose any calibrated settings due to unplugging and/or moving your television. Most likely, if they calibrated it, the settings would be stored under an "Expert" video setting (other settings being things like "Vivid" "Standard" "Sports", etc). Perhaps it went back to "Vivid" or "Movie" or some other setting and you simply need to change it back to the one they used. If everything is dark, it most likely isn't on "Vivid".
When I bought my plasma, I found a calibrator through the AVS forums. He came down from Canada to my house and spent about 4 hours working on it. Explained everything he was doing, showing how the changes he was making were affecting the picture, etc... Gave me a printout of all the exact settings he ended up using.
Calibrating yourself can be a tricky thing. Usually instruments are involved that require a little knowledge to use. There are DVDs out there to get a general calibration done, and I've heard some good things about them. Those will most likely do just fine for you. Hopefully you get your set back in tip top shape.
