Hello,
See
Successfull Replacement of M3 broken display
I started the disassembly from the bottom of the M3 with the pray tools that was delivered with the replacement screen, a thin flat screwdriver and a creditcard-like piece of plastic.
I bought the replacement screen at ebay to a seller called bureenz, the name of the part I bought is
"LCD Screen Replacement for 2nd Gen iPod NANO 2|4|8GB 2G".
Hope this helps