Buyers market on Explorers. Gas prices are killing sales, so drive a bargain thats much better than you expect and you may very well get most of it. Just be ready to walk away to force the issue - there ar many exs for sale, you will have no trouble finding another.
The 02's on are known for tranny and differential issues. You will see quite a few posts on here bout those.....
If it were me, I'd go for the 100k extended warranty, but make sure its a good warranty company. Ford, Daimler Chrysler seem pretty good. Do not buy a "stated coverage" type aftermarket contract.- all the high tech stuff on the ex will not be listed, therefore not covered. Thats a simplification, bur not too bad of one. Stated exclusion contracts are safer - they list up front what they do NOT cover. So you can see what your out of pocket risk is.
In this market I'd demand the warranty be thrown in for free. If you get the warranty, you get a lot of truck for a very good price in this market. Check KBB here for the dealer wholesale value and get as close as you can when you buy it.