I just had a Melling HV pump installed in my stroker last month so I can tell you exactly what's involved.
In my case, I had to clearance the oil pan to fit around the HV pump yet some guys didn't need to do this. Here's my write-up:
http://www.angelfire.com/my/fan/HVOP.html
If your Jeep has a suspension lift, getting the oil pan off is a lot easier. If, like me, you have stock height suspension, you'll need to do the following:
1. Disconnect the negative battery terminal
2. Jack the Jeep up by the frame rails and let the front axle droop
3. Drain the engine oil and remove oil filter
4. Disconnect the front shocks from the lower shock mounts
5. Remove the starter motor and solenoid
6. Support the front of the engine under the outer part of the harmonic balancer (not the grooved part) with a jackstand
7. Remove the engine mount bolts
8. Raise the front of the engine with the jackstand
9. Remove oil pan to block bolts
10. Gently pry away the pan from the block with a wide paint scraper
11. Have fun scraping away the old gasket material and RTV from the block & pan mating surfaces
12. Remove oil pump with pick-up (only two bolts)