Saul, your truck must be a single cab, the window setup on those is completely different than an extended cab 86-97 and 1998+ Rangers.
I paid $23 for the tinted rear slider in my truck. But I have an in, so you can expect to easily pay $30-$60 for one at the higher class rip off yards.
What you need to do to remove the rear window from a 98+ Ranger or an 86-97 Supercab is first the trim needs to be moved out of the way to gain access to the 8 nuts that hold the window in place. This is easily done by pulling the clips out, and then either pulling them all the way out and removing the trim, or just getting the trim far enough out to gain access to the nuts. You will also need to remove the coat hanger from the roof. Next you'll need to remove all the nuts. There are 3 on top, 3 on bottom, and one on each side. I suggest saving the ones on top for last, just in case the old seal has dried up for some reason. Once you get all the nuts off, gently push the window outward, pushing evenly around the window to prevent possible distortion. Eventually you should have at least one spot that is out enough for you to get your hand through. I suggest only pushing out one spot. This way you can then get out and hop in the bed, and then better support the window while you're removing it. If you have someone else to help you, this is not needed as they can be in the bed supporting the window. Now push the rest of the window out. You will need some kind of sharp object to cut the adhesive webs out. After a little bit of pushing the window should be out. The junkyard window should be out, and now you can use this same method to pull your original window out. Once you have your original window out, take some alcohol and get all the old seal off of your cab surface, as well as the new window. Once this is done you will need to install your new seal. The seal I recommend is the 3M ribbon sealer that you can find at Advance Auto Parts. I'll add a link to it at the end of my post. Once the new seal is applied, knead the seal onto the window to make sure it is fully seated. Now pick up the window and insert the threaded posts on the window back through the holes in the cab. Gently push around the entire outer edge of the window to be sure the seal sticks and get the window as flush to the cab as possible. Then, get inside the truck and put the nuts back onto the threaded posts, and tighten down hand tight. You may have to get in an out of the bed a few times to push on the window to get it to sit flush. After you get all the nuts tightened down, do the water test. Run a hose around the window to check for leaks. If none are present, then re-install trim and clips. If leaks are present, get in the bed and try pushing around the window again, and checking the nuts. Do this until no leaks are present, and then reinstall trim. Now, you should be done. If you're install goes anything like mine, you'll have the old adhesive webs all over your cab and bed, so you'll need to clean this up. Rubbing Alcohol works wonders just as it did for your cab/window mating surface.
Hope this helps man, if you have any further questions, PM me.
Link to recommended seal:
http://shop.advanceautoparts.com/web..._T|GRP2034____
Link to How-To written by Jazz921:
http://www.fordrangerforum.com/how-s...w-98-09-a.html