Well I'll go ahead and answer my own question I guess for posterity...

98 Explorer EB 4WD.
I ended up ordering the new power mirror off eBay with heat and light (even
though I only had the puddle light on my old one) as I figured I could make
the electrical connector work even if I had to splice it.  To make a long
story short the electrical connector was compatible and the mirror works
fine. I now have a heated mirror as well as a bonus as it appears the
electrical was in place for it in my EB.

Ordering the part off eBay (http://stores.ebay.com/ALL-NEW-PARTS-STORE) was
painless and cheap ($21 USD + shipping!) so I'd definitely recommend them.
Replacement was easy:
   - Remove inside door panel (with window down) - 2 screws and some push
pins
   - Remove speaker to disconnect mirror plug behind it
   - Remove 3 bolts holding mirror on (don't drop them in the door!)
   - Reverse above