Taken together, those threads answer your question. You can swap to a full instrument cluster just by bolting it in and changing the temperature sender and the oil pressure sender.
My XJs are old enough to have mechanical speedometers, so I am not certain what you would need to do to retain your current odometer reading. The new speedometer will read okay, but I don't know if the odometer reading is stored in the instrument itself, or in the ECU. Your '96 is the first year Chrysler used OBD-II on the XJ, by the way, so that might make a difference. For that reason, I would try to go with a '96 cluster even though 91 thru 95 also used an electronic speedometer. I don't know if the 91 thru 95 will be compatible with the '96 electronics.
In a worst case, if the odometer is way off after the swap, just swap your old speedo/odo head into the new cluster.