1. Get some sort of file syncing tool to copy your files, with no modifications to their dates, times, etc, over to the new location on the NAS. Make sure you have them copied correctly. Do a some testing to reassure yourself.
2. Make an MC backup of the database: File > Library > Backup library . Take note of where this file is saved.
3. Use the RM&C tool in UPDATE DATABASE mode.
A. Use the find and replace template to change the drive letter. Something like :
Find: G:\
Replace: Z:\
B. Look at the preview window and make sure that your find and replace is doing what you want it to do.
C. Press OK when you are sure.
For step 3 above, you might want to try doing just one album first. Then do some more. Then do them all when you are sure.
If you get things messed up, use the backup you made in step #2 above to restore MC's database.
I've used this method, mostly on my Macs, dozens of times. It works nearly flawlessly. As far as I know, the only things that won't be updated via this method are:
* Particles
* SACD ISOs individual tracks
* CUE file based albums
Other than that, your library should work the same as before, just on a different drive.
Best of luck,
Brian.