replacing a driver

My wife was supposed to pickup a nice older used Sony cassette deck for me and came home with a pile of everything but that. Anyway, in the stack was a Sony STR-D665 receiver. Not that great but thought I could setup and friend or family member... But the left channel on both the A and B speakers is about have the volume as the the right side. I asked my repair guy to check it out and he said it was the driver and wanted $45 to do it. Since this does not even have any digital inputs, I decided not to have him fix it. But now I have another amp I am not using sitting around and thought of trying to do it myself for fun.
Can anybody point out the location of this part to me. I am sure the part itself is cheap but I don't want to order it till I am sure it is something I can swap out myself and don't know where it is. Here is a link to the repair manual if that helps. Thanks in advance.
SONY STR-D565 STR-D665 Service Manual free download, schematics, eeprom, repair info for electronics