I haven't read of anybody just replacing only the glass yet. But I have managed to replace only the glass and it works!
I fell skiing at Heavenly on December 27th. The Gorilla Glass did not survive.
I bought the glass from eBay that same night http://www.ebay.com/itm/250958153617...#ht_1340wt_958
for $4.99 + $4.99 ship from an Australian distributor. I arrived today and I started working on it at 1pm. I searched YouTube and found a bunch of videos on how to remove everything up to the digitizer and glass assembly, but nothing after that!
At this point I cracked open the phone and followed the video thinking there was more. The logical think to do would have been to watch the video all the way through at first. And I guess since my SGS works, I'm fortunate that I didn't!
The glass on the phone was completely shattered with no pieces larger than dime left whole. So I started around the top edge first. Once I gain confidence on separating the glass from the thick layer of glue using an Olfa L-2 knife, I started in on the capacitive buttons. Here the glass had shattered to pieces about 1/16 - 1/8th of an inch, relatively easy to remove using the knife to at first wedge, then pry upwards. Both buttons work fine, but I was really careful and it took a bit of time to do. Thinking that was the hardest part was foolish thinking in hindsight...
Clearing the rest of the digitizer is a chore I care not to do again. But it is possible! It took about 3 hours to remove every sliver of glass. As it is like safety glass, it shatters into fragments easily. And once that's done you need to clean up the glue, laced with fine glass dust that can potentially scratch the digitizer. I did it with 50% alcohol and polishing compound. It took the better part of an hour, but it was the only thing I had around the house. Somebody mentioned ethanol on this thread, I'd go with that instead.
You will see a few nicks and scratches on the digitizer. I was will to accept this since I am eyeing a Galaxy Note and this phone is going to to be permanently stationed in the car (the Torque OBDII app works like a dream, it has GPS, is a web browser and plays music though my bluetooth car audio, and can share the 3G data plan. Name a head unit that does all that?). And in all honesty, with the glass installed it looks better than I expected.
To install the glass I used double-sided tape. I heated up the tape with a blow dryer when I sealed everything up, and pressed firmly on all sides to insure a good bond. I was disheartened to find that the digitizer did not respond to every touch. Turns out this was the effect of the warmed glass. As it cooled the touch response time got back to normal. Also be careful of over heating the glass and pressing too hard on the corners of the digitizer. I have a red spot in the edge of a corner I pressed. If I were to do it again, gluing (the type discussed earlier in the thread.) would be the way to go. Finally finished around 6pm. And everything works!