Personally, I wouldn't use MC to move files from drive to drive. The Rename, Move, and Copy tool is *awesome*. But when it moves files, it doesn't give status, which makes it really hard to track what's going on. I would do it like this, as a high level overview:
1. Use rsync, robocopy, or some other file copying tool to copy your 8000 files from drive A to drive B, preserving the EXACT SAME directory structure. Example source and destination:
Source: F:\Music\Pink Floyd\Dark Side Of The Moon\01_Breathe.flac
Destination: G:\Music\Pink Floyd\Dark Side Of The Moon\01_Breathe.flac
You could add some top level directories like G:\New\Dir\Here\Music\Pink Floyd\... but try to keep it simple for the next step.
2. Use the Rename, Move, and Copy tool in Update Database mode. This will let you change the location that MC knows for all of your files to point to a new location. Use Find and Replace to change the drive letter and maybe a top level directory or two. Wiki article for reference:
http://wiki.jriver.com/index.php/Rename,_Move,_and_Copy_FilesAs the previous poster said: Start small. Do some experiments so you can learn the tools and figure out a method that works. Then do some more. Continue using larger batches until you're done. Validate your work as you go. Use the Preview Pane in the RM&C tool before you press OK.
Good luck!
Brian.