Regarding the IBM Blu Ray Drive, which I ordered for under 400 on ebay and have in my hands...
1. Yes it is the Panasonic UJ232A
2. It is the same form factor
3. It has a plastic piece on the back that screws off, you then take the mounting bracket off your exisiting drive on the M6400 and screw it in its place
4. However - the Lenovo faceplate for this drive extends beyond the edge of the M6400. I find it annoying enough to put the other drive back in until I can get a M6400 UJ232A faceplate. Any ideas on part numbrs would be nice.

Hope this helps.
Jim