The wiring is pretty straight forward but there will be a couple "gotcha's"
The PATS system between your Expo and Ranger are different, you'll need to graft in the Expo's PATS module and work out a way to re-use the Expo key(s). (Couple options there)
The speedometer signals are another issue. Your 01 Ranger expects it's speed signal from the PCM, the 01 Expo expects it from the ABS system. So, put both together and you've got NO speed signal at all! Grafting in bits of the Expo ABS system is the common solution but adding in an earlier VSS or a 4 cyl Ranger GEM are also options.
A couple great reads that cover most issues:
Everything you wanted to know about PATS. - Ford Explorer and Ranger Forums "Serious Explorations"®
Swapping An Explorer 5.0L In To A 1998-Up Ranger
2001 Ranger 5.0l Swap Wiring Guide!!!!