card reader needs to be replaced

Replacing the CF pin FPC assembly is a bit involved, since it requires removing the main PCB board to gain access to it (which involves disconnecting a lot of ribbon cables). Fortunately there is a guide available showing how to replace it for the Canon 7D. Note that you may also have to go one step further than the guide shows. The CF card slot has a metal enclosure, but most of the replacement parts you'll find doesn't include this enclosure and only comes with the pin assembly. This means you'll likely have to remove the two screws that are holding the metal enclosure in place so that you can reinstall it on the new part.

Based on a quick search, it seems like a replacement part is going to cost you roughly $50, though you might be able to find someone overseas that you can get it from for cheaper. To aid with searching for a replacement part, the part number is CG2-2544 and the part name is CF Pin FPC Assembly.