If its clean, 4x4, and has had good maintenance then id do it.
I actually thought very seriously about picking up a 07-08 explorer which is the style after that 04 but with all the little issues some seemed to have I decided not to; but imo the year grouping your looking at there are pretty solid and about the same to maintain and repair as your ranger. I decided to look into getting a 07/08 grand cherokee QD2 hemi with 30-60k miles as we speak but thats more because I have to stick to an 07-08 grouping, and the jeep seems to have more to offer and alittle more reliable than the explorer's of those years (also auto LS lockers front and rear, more power with same if not better gas mileage and towing, tons more room and comfort, the aftermarket is tons better, etc makes it much more appealing than the ford. The only thing the expo of those years has better to me is the ford brand and im a big fan of its styling inside and out!) But thats getting off topic and is different than your year grouping explorer and your issue at hand.
While it doesn't have a bed, in all honesty you will enjoy having the inside room, comfort, etc over having a bed. It sucks that you lose your bed space, but in all honesty I don't use my bed THAT much to justify it. Plus your lowering what you owe and payments which is always a great thing, financially and just from a comfort standpoint.
If I really need a truck bed, ill use our 06 dodge 3500 or my old beater s10. As much as I liked my ranger, an suv is a better fit IMO, and lets be honest if you really needed a truck all the time, and your always using the bed say for your job or rough work, you probably wouldn't want it to be in your brand new ranger anyways. If you really need a bed that bad, take some of the money your saving and buy a beater to use.
But the most important thing and what it should all ride on is the condition of the explorer and if its 4x4, because while you can't predict the future, you'd hate to do it and then have nothing but problems with it. Hind sight is 20/20 but if all things being equal to each other, and following what I have already said, id do it with those conditions.
Goodluck.
