I once had to change over doors on my last Omega, basically its just the lock mechanism you got to change. CHECK FIRST that you don't have side impact air bags, as these would need to be disconnected first, otherwise they might go off.

If memory serves me right, a couple of screws to hold on the handles, not forgetting the lock button that has an insert to lever out to get it off, then remove the door card (screwdriver under and lever gently!), . Then I think there are 3 or 4 nuts holding on a diecast mechanism that has the lock barrel and a couple of pushrods, that are clipped in place with plastic clips, that just turn 90deg to release. Somewhere in that lot is the lock barrel that you change over. Sometimes with older type locks, you can pull out the actual 'fingers' that detect the lock profile, and could change them over, so you might be able to rework your replacement boot lock to work on your old key, thus saving you having to do the doors.
