I put the back window in today. Cutting and stapling the opening went easier than I thought it would. One of the tricks here is to use two hands on the stapler, whenever possible -- putting one hand on top, directly above the driving mechanism, keeps the stapler from kicking back and helps drive the staple more deeply. I didn't have any trouble getting 1/4" staples driven flush with my electric stapler.
Putting the window back in took my helper and I three tries. The first attempt I used garden twine, which was obviously not up to the task. The other two I used 1/8" nylon rope, which worked much better. A tip -- when inserting the window, put the top edge in
first, as it's the hardest to get seated. Push it in as far as you can from the outside before you start pulling on the string. Have your buddy follow you around as you pull on the string, leaning on the outside of the window next to wherever you're pulling. Soaping up the inner seal lip good before you start helps, too, but in hot weather the soapy water is going to evaporate before you're halfway done.
Since people keep asking for pics, here's the finished window:
http://www.gull.us/photos/automatic/ind ... g_1023.jpg
I probably should have taken a picture of the opening before putting the window in, but I didn't. It's really pretty obvious how it works when you take the old top apart. Instructions differ on whether you should cut the top to the shape of the opening first, or not. I chose to cut a big X inside the opening, so I had more material to grab onto as I pulled things into place. I made relief cuts at the corners as necessary, then after I had all the staples in I ran a blade around to trim off the excess material.