There's no easy answer. The FSM talks about doing it when still in the vehicle, but that's at a shop with a lift and other specialty lifting/support tools to make the job easier.
For guys like me, it means putting the vehicle up on 4 jack stands, raising the motor up from the harmonic balancer to get enough clearance to slide the pan out and then getting the work done.
If your doing the timing chain too, I think I would consider pulling the motor just because you are already moving stuff out of your way to get to the timing chain.
If there's really nothing wrong with the pan and the rear seal isn't loosing lots of oil, I'd just do the timing chain... but I don't know the situation.
__________________ 2008 Jeep Wrangler X (Hard Top)
Incubus Off Road 511's with BFG 285/70-17
1998 Jeep Cherokee Sport
4.0L/AW4, Yakima Roof Rack
You must do the oil pan gasket when replacing the timing set because the timing cover must come off. I just hit this wall after blowing a timing cover gasket. And I have a seeping rear main seal, which is a bear to do when on your back. The harmonic balancer needs to come off too, so you need to pull the radiator to keep from mangling it. After careful thought, the motor comes out this weekend.