I think I may have found the answer to my own question...this is a TSB from 1998 but I would think the 5r55E Ranger/Explorer trans hasn't changed much since then.
Full Text Technical Service Bulletin
Drew a little fluid out and got it right on the halfway mark between the bottom of the hashmarks (low level) and the first hole towards the bottom of the dipstick from there. The truck has been in the garage all day and last night, not driven, and its about 52 degrees in there so I should be right where I should be as far as the fluid level.
I used this guys idea for extracting some of the fluid. Worked well and I can use it in the future for exchanging a quart or two of fluid during an oil change. The bleeder tool was about $29 at Autozone, the new tubing and barbs was about $5 at Lowes, and I used a Mason jar and lid we already had. Good idea!
Heres the link:
YouTube - How To CYCLE TRANSMISSION FLUID In Your 02-07 Jeep Liberty 3.7L