Umm, i got a '98 F-150 XLT Ext.Cab and the back seat folds down, but does the seat back fold down? I'm not sure. I'm scared to pull to hard and break something. It just occured to me while i was sitting here. Also, i don't know where my jack is, so i'm assuming it's stuck behind there somewhere. I just bought it so i haven't discovered everything yet....obviously

 

Seat back does not fold down. You should find the jack under the passenger seat. The handle will be in the engine compartment running across the top of the radiator.

 

There should be a little black cloth handle thingy near the seatbelts in the rear seats. This should take down the bottom of the seats, but you are on your own getting the top to come down.
BeastRider is dead on about the jack and the handle!