Installation by Best Buy or CC will be excessively pricey because you didn't buy the merchandise there. I've had installations done by Best Buy and they were good and fast, but they may be pricey. Like others have said, find a local installation service and get it taken care of there.
Although, personally, I think that if your speakers are the same size as the fittings into which they will be installed, it shouldn't be a problem installing them yourself. There are only two or three wires that plug into each speaker, and it should be a simple matter of removing them from the existing speaker and fitting them to the new ones. HOWEVER, if they aren't the same size as the fitting then just forget about it and get someone else to take care of it for you.