Is whole MK IV fried or is it just a dead drive?

[bmwnavnewbie]

My nav quit working yesterday (coincidentally while car was on Deltran Battery Tender Jr.) and I got the typical black screen with occasional horizontal white flashes. Couldn't get the DVD out, and the DVD drive acted differently than it ever has - usually when it can't read a disk the power light stays on and it keeps trying for awhile, and it tries to read the disk when the trunk is opened. It was giving up much more quickly this time. I opened up the unit, lifted the motor, and got the disk out thanks to the nice instructions at

http://www.xoutpost.com/articles/all...ion-drive.html

Reconnected the unit (with no disk in it) and still get the flashing nav screen. Normally with nothing in it, it should say "No CD/DVD". So I'm wondering if it's likely that the electronics that are not on the DVD M3-4.6 drive module are dead, or if there's a good chance that the DVD M3-4.6 replacement will cure the problem.

Anybody have similar experience and/or have an opinion whether a drive replacement will fix it (obviously that would be the least expensive solution)? Any chance the battery tender connected in the engine compartment would have affected the DVD player in the trunk (should be some voltage drop from front to back)? Doesn't seem like the battery tender voltage is any higher than alternator voltage.

Thanks very much for the help.