No fabbing for the nv3550. I bought mine just over a month ago for 500 and another 500 for all the conversion parts from advanced adapters. I would say the swap work wise will be the exact same. Its just a matter of what you kind find for the price of the tranny. The nv is a stronger tranny with better gear ratios. Just do a search for each one. They are compared a few times on the site. For my swap i unbolted the ba10 and cranked up the new nv and bolted it in. It is a direct swap. For either swap you will have to change the input gear in your tcase. That is it in a nut shell.
Its not a jeep if it dont have 4wd.