I don't think that its possible but correct me if I'm wrong. The drive is quite integrated into the casing and its a slot loading drive so even if it is possible i think it would be difficult. :S
Bump... does anyone else know if this is possible? There's nothing on the macsales site about upgrading the cdrw drive to a dvdrw drive in my CD macbook 1.83.
Anyone know of a solution other than the fastmac blue ray drive?