My back window fell out!
 

My 2002 986 S is in the shop for some routine work, and today my mechanic reported the back window had fallen out. Fortunately, it was parked inside, and even more fortunately the window wasn't broken. (This car had a top replacement before I got it, with a glass window instead of the standard plastic.)

So, what's next? Is this a DIY thing or should it go to an expert? Or will I need an entirely new top?

I had one that was starting to come loose. For about two years I tried adhesives, but it kept coming apart. In the end I replaced the top.
If the whole window is out, you can try 3M double sided automotive trim tape. It works better than most glue type products will.