Replaced hard drive cable for unibody 15" late 2008 MBP
The MBP started freezing up and giving all kinds of errors. I did a clean install of OS X, but I didn't help. I then read on a number of forums about folks with my same issue and it pointed to a bad hard drive cable. I determined that it wasn't the drive by removing it and placing in an external case - booting and running the computer from there for a week - no more freezing issue. So I knew it had to be the cable.
The process was painless. I meticulously followed the ifixit repair guide. I was very cautious with removing cables, so as not to damage anything else. The disassembly was easy. I just made sure each screw set was segregated into separate bins so that reassembly would be easy. The only nerve wracking part was reconnecting the micro-sized connectors. I was concerned with bending a pin or not getting them seated completely, which would render the camera or optical drive inoperable - I really didn't want to disassemble and start all over. But to my amazement everything worked perfectly after the repair was done.
Move slowly and methodically. Keep screw sets in separate bins. Be gentle with connectors. Follow the repair guide exactly as instructed. Don't drink too much caffeine beforehand. :)