Thinkpad 570 and DVD burner

[kfir]

Hi,
I want to buy a dvd rw for my thinkpad 570.
I have ultrabase with cdrom.
I'm working with linux, but i think it would'nt do me a problems.
If i want to buy oem drive, how do i know it will fit my ultrabase?
I can remove the plastic from the cdrom and put it on the dvd.
I want to buy it at ebay.
How do i know if dell or toshiba drives will fit?
tnx