jeep is leaking from the differential cap i guess its called the question if when i replace it will oil pour out and if it does how do i replace the oil that was spilled or would it be easier to take it to a mechanic?????

by differential cap, i assume you mean diff cover? if so, with a catch pan, undo all the bolts leaving the top one in and somewhat loose, then with a mallet, tap the cover to swing it to one side. catch all the diff fluid that you can, then i use brake cleaner to clean out the inside totally. when it's all clean, inspect the ring gear and carrier caps, etc.
then scrape what gasket/rtv you can with a scraper. then for what's left, i use a drill with a wire brush to clean the gasket surface, then throw some ultra black rtv all around the surface and mate the cover back on. then wait for about 20 minutes for the rtv to set, then fill it up through the plug on the diff cover. front d30 uses a ratchet with no socket to remove it, and the rear d35 i believe is just a rubber plug.
they take about 1.5 to 2 liters each of 75w90. if you have clutches (lsd) in the rear, use a small bottle of friction modifier.
if the new gear oil is cold, you can warm it up to ease the flow.

hope that helps

how ever if you are talking about the plug located about halfway up the diff cover it may need to be tightened on the front and for the rear on D35's and 8.25's it is a rubber plug that would need to be replaced by a dealer part

thx for the info guys really helped both of u hit it on the spot ill fix it tomarrow