I just found out how to upgrade your DVD-ROM Drive.
You need a "One Highfly mobileCombo CDRW/DVD ROM" Drive and a normal built-in Apple DVD Rom drive.
-Pull out the DVD ROM drive and get the screws out of it.
-Isolate the drive from its platform.
-Now open the Combo Drive
-Remove the drive from the plastic exterior,
both drive have to look nearly similar
Now remove the chip-unit stuck to the Apple drive and place the "One" drive on the Apple Platform
-connect the cables and put the screws back in
-now you've got a new DVD-ROM/CDRW drive
Sorry for my bad english.