They are removable, in fact, most now besides intelgrated mobile cards are. There is, however, some slot compatibility problems with MXM, where a card will fit a certain MXM (in my case, type III, I believe) and not fit the new MXM Type A or B. It gets really ****ing complicated. It is, however, easy to tell if it will fit or not, the types of MXM connectors on the card are distinctly different between the types, except between MXM cards that are larger but have the same connector (MXM type A has an identical MXM connector as MXM type B, but type B is longer iirc).
pro-tip, they've been removable and interchangeable for years now.
EDIT: And I forgot to mention that most laptop hardware is removable too, including the mobo. Though if the mobo is interchangeable or not, I do not know.
Actually I wish I had just gone with a newer model, one of the 2009 or 2010 models with the new MXM though the 2010 models can use the i7 cores iirc.