I did mine in a couple hours. Went to Autozone and I think the new (well refurbed) motor (theres only one, it links to both wipers) I bought was $95. Theres really not too much to it.
If I recall correctly (bear with me, I did it last year):
1. Remove the wipers from the post (replace post with technical term). There is a c-stlye clip that holds them on I think.
2. Open the hood, there an 4-5 screws, horizontal (probably under the weather stripping just below the hood hinges. Undo them, they hold the rectangular body panel over the wipers and behind the hood. I think I had to close the hood to get the panel off.
3. This is where I get a bit rusty on exactly what I did.....Obviously you need to disconnect the ruined motor. Pay attention to how it was connected.
4. Plug in the wiring harness of the new motor. Mine didnt match colors like it should (I think 3 or 4 of the 6 did), so I went through a couple fuses guessing which went where. Actually I think maybe the wiring harness didnt work and I just used wire joints.....
5. Test and make sure they are turning, including that the variable speed works.
6. Assuming it all works out, replace the body panel, screws and wipers and you are good to go. Probably saved at least $75-$100 by doing it yourself, not to mention getting to know your Jeep better.
Hope this helps.