My daughter dropped our iPad2 and the digitizer was shattered. I knew this was a common problem, so I started doing some research online to find the right parts and advice for the repair.
Removing the old shattered digitizer was a painstaking process - even after heating up the adhesive areas with a hair dryer, every time I worked the tool under the partially shattered areas, the glass in that area would shatter more or even powderize. Consequently, it took me an entire evening to remove the damaged digitizer. The difficulty was extended when my tool slipped and tore the volume/power control flexy cable necessitating the need to order a replacement and wait until I had it to continue. Patience . . .
Be sure to clean all of the previous adhesive from the frame of the iPad before sealing in the new digitizer. I used some nail polish remover and cotton swabs - don't put too much fluid on the swab tip, use just enough to moisten the glue before you rub it off with the tip of the swab.
Also, be sure to apply the adhesive to the glass, not the frame - it makes it easier to seat the digitizer. ifixit has a great image showing where each segment goes.
Be careful of the cable connecting the digitizer to the mother board - it's easy to put too much tension on it while applying the adhesive strips to the digitizer and it can be partially damaged so that you will have dead spots on the dither, but not know about it until everything is sealed up.