Definately check the rocker(valve) cover gasket! My '93 xj was leaking horribly so, I went ahead and did the rear main seal. Pain in the butt! Only to find the old one looked pretty much new. Put it back together. Same leak! Later on, while planning to get a newer 4.0, I discovered that the gasket was hanging out at the rear of the cover! Dumbass!
$8.00 dollars and ten minutes later, nary a spot of oil on the driveway or on the rear glass!

'Tis not the critic, but the one in the arena who matters.

'61 Willys truck,(runs but won't stop)
'93 XJ 3" rubicon, sliders, under armour, front and rear bumpers, 31's, snorkle, 60" hi-lift xtreme, other stuff.
'00 XJ stock
'03 Grand Cherokee