Before you try and rebuild it, you can reflash the touchscreen chip. This has fixed the problem for me when Android crashed a few times. ( The above may be the same but I already had most of this process written and saved in case someone ever needed it.
In case you are not one of us die hard TP users, I am going over everything, Skip what you already know/have.
Your TP needs to be in dev mode. If it is not, the below will not work. Since your screen is inop, you won't be able to activate it. (Maybe unless you have a TP bluetooth keyboard paired.) Someone please chime in with help in case this is the situation short of re-doctoring ( If you do, type webos20090606 in the just type box and click on the dev mode icon. Turn it on without a password and close it. Now dev mode is on for future use.)
If you do not have novacom installed you will need to first modify your hosts file: Looks like you can't get the SDK anymore (almost)
Then download the program here ( 32 or 64 bit depending on your system: Can’t Download Novacom Drivers for Windows to Connect HP Touchpad | Sheldon's Blog .Com
Once installed go to C:\Program Files\Palm, Inc\terminal and click on novaterm.bat to open a terminal window
1. Connect your TP to your PC
2. Launch Novaterm, click on File- Connect to connect to your TP.
3. From the command line type each line below exactly (Press enter after typing each line.)
A lot of letters and numbers will fly up the screen as the touch firmware is reinstalled. After it completes:
Disconnect the TP from your PC ( FIle- Disconnect)
Your touch may return immediately or may require a reboot. In my case I have had to run the above a few times to get the touch to respond but so far it always has.
If all of this fails, you will need to open your TP and replace just the digitizer. It simply unscrews from the LCD and is connected to the system board by only 2 flip connectors. There is a plastic bezel that is connected to it with some double sided tape that you can get from amazon.