I have done it. My recommendation is to spend the two hundred bucks.
Let's start with removal. The windshield is very securely glued in with a urethane sealer. In theory, you can get the old windshield out with either a specialized hot knife tool, or with a piece of fine piano wire. The wire method is laborious in the extreme, and best done with two people. Expect to use many pieces of wire. It will break. You can also use thin flexible blades, such as hacksaw blades ground to an edge, for some of the work. Even then, it's a battle. Eagle and I got one out together a couple of years ago. No tears as I recall, but plenty of sweat, and some blood. It's very easy to crack the windshield getting it out, and even a little nick in the wrong place will undo a lot of work. Finally, of course, most used windshields are just that - used, and that means pitted, scuffed, etc. If you have a parts vehicle anyway, go ahead and try it, but if you have to pay, I'd say forget it unless the windshield comes pre-removed, and then it's possible the cost will make it less of a bargain.
For reinstallation, of course your first job is to cut out your old windshield in the same way as you salvaged the new one. Resist the temptation to smash it out, because you'll still have to cut the bead very carefully, and all you'll have gained is a lot of cleanup and almost certainly a fair amount of stray blood. First, of course, you need to remove the trim, if you have an older XJ (this is metal trim held on by tabs that are easy to break). Be careful. If it's a later one, it has a plastic surround that is installed over the glass before it is glued in. It's hard to salvage this, but it can be done if you cut carefully enough. The windshield will probably have to come off with the new-style trim still on, so you'll take a few chunks out of it, but it might still be reusable. Otherwise, I think it can be replaced, but add another 30 bucks or more to your cost calculations. This is strongly recommended as an upgrade for any year. If you have done the cutting right, you'll have a layer of well-adhered original sealer left on the vehicle after you've sliced out the old glass, about half the thickness of the original bead. Leave that there, cut off any obviously high spots, and then lay another bead of urethane on top of it. Make that bead nice and fat, and as even as possible. Take time to insure there are no low spots. If you're using or reusing a late-model trim ring, put that on the windshield, make sure the windshield is clean of grease and grunge, and lay it on the new bead of sealer. There should be a couple of little rubber blocks still in place in the window frame to help keep the glass from going too far off center or sliding down. Press it in gently, and try to make sure that it is in contact with that bead all the way around. Make sure it is centered well, especially if you are using the old style trim. Second chances are messy and expensive. Don't press too hard or unevenly on the glass, even if you think you've got a sealing error, because it's easy to crack it. You can sometimes work it tighter by wiggling a little on it, but basically, if you didn't get a good fat even bead of urethane to start with, you lose. You might be able to seal it later from inside, but it will probably always leak. Any more than a little gap may be unsafe. The windshield is a structural element in the vehicle, and you really can't afford to have it fall out or pull loose.
Extra rules apply if you find rust under the sealer, or the sealer has lifted off the metal, because you'll have to repair that, and apply sealer to build up the area you fixed, or the windshield will leak. It is also possible to remove all the old sealer, but the soft urethane that comes in a tube will be hard to build up high enough without a terrible mess. You can also buy a preformed bead of stuff that you lay down instead, but this may not do a very good job of adhering the windshield, and I don't recommend it for safety reasons. I haven't researched the latest products and prices. You might have to seek advice from body shop or a very well informed parts-store guy for the best solutions here.
Unpredictable extra rules also apply if you find that you're not the first to replace the windshield and a previous job was badly done, with either the wrong sealer or a poor application. You may end up needing to redo the whole thing from metal out.
When you undertake this job, try to estimate the expenditure of time, and also make sure you price the glass, the trim if needed, and the adhesive. Calculate this on a "can afford to lose" basis. It is certainly possible to do this job oneself, and to do it well. I have done it a couple of times on different vehicles and been happy with the results. But I cannot stress enough that it is also painfully easy to blow the whole effort with one push, nick or tap in the wrong place. I have done that too! So calculate not only what you can afford to do, but what you can afford to do twice.
edit PS: The factory manual calls for urethane adhesive. I am pretty sure that others are not suitable for this job. According to the FSM, even if you remove all adhesive back to the pinch weld, it should be replaced only with a bigger-than-normal bead of urethane, not butyl or other stuff.
