I don't know if there is a step by step guide, but it is pretty simple.
Buy an NP242 transfer case, shift bezel, shift gate, and full-time light wiring harness of the same era as your XJ. Based on your signature that would be a 97-01 XJ. Note that other vehicles may have the same basic case but will have different mounting holes or other changes.
Remove the NP231, and install the NP242. This is easier if you remove the crossmember (support the transmission with a jack) but not necessary.
Remove the NP231 shift bezel and gate and install the NP242 parts. Adjust the shift linkage under the floor, leaving some room for play in the handle when it is all the way forward and backwards.
I'm not sure about the 97+ but on older models you had to install a bulb for the full-time light (factory part-time did not have a bulb in the full-time socket), and also required a different wiring harness to connect the transfer case switch to the light (
more info).