I have an 01, with 105k on it. I replaced my lift pump at 80k. It didn't just die, i would take off from a light and would not have power because a symptom of the lift pump going is no turbo. But if i shut the truck off and restarted it would start working again. That lasted a couple weeks before i actually had it replaced. (don't try towing like that)
20k on a cummins is nothing. But the trans will run you between $3,800 - $4,500. Mine is on its way out. doesn't slip but doesn't ship very well. 2-4 stall and normally end up pedal shifting it. I have talked to a couple different shops and done a decent amount of research and came up with, do not have yours rebuilt. Have an ATS put in and make sure you replace all the lines at the same time.
The only other issues i have had was the front end. I am on my third set of hub bearings and 2nd set of upper and lower ball joints.
with all that said i would still take my dodge over a ford or chevy anyday
85 CJ7 begging for a restoration
92 YJ 4" RC, 4.11's
01 Dodge 2500