when i did mine , it was easier to jack it and put it on stands to get it out ,but i lowered it to get all the old fluid out and finish the job.
one other thing to check is just make sure the leak is comming from the gasket itself before going through the work . I had the diff vent plug up on me causing oil to be pushed pass the rubber gromet and because my diff was alwys so dirty all the time from the mud & gravel roads , i thought my diff gasket was leaking .
Proud owner : 05 WK Ltd 5.7 HEMI
90 YJ Islander 4.2 Cam'd & Decked
94 ZJ Ltd 5.2
00 WJ 4.0 - new to me Aug/13