97 XJ, the doors are easy, be carefull not to force or break the plastic rod clips. Below the ign cylinder facing the floor is a small tab, inset the key, press the tab, and turn the key. At some point the tab will push up and the ign cylinder can be pulled out using the key. The tail gate lock is held in by a U shaped clip. It may be easiest to get the complete tailgate handle assembly and just swap that over instead.
If the 90 is the GM style steering column search the GM forums for info.
I have a complete set of locks and keys for sale, PM me for details.