I've searched through the forums and on the write up in project jk, but I can't seem to find whether there was a gasket used in the write up or if the old one was reused or a new one, as there was none listed.
I've read mixed reviews on lubelockers. Maybe it's better on the trans than the diff. I used Right Stuff 1 minute rtv on mine. Be careful not to overfill it with fluid. I got confused by the weird process of checking the fluid level, went way to far over, and boiled a bunch back out of the tube and had a lot of slipping issues until I pumped 3/4 of a quart back out.