Hello and welcome to Android Central. If you are looking to do this yourself, fixez.com sells the digitizer and screen kits. There are a few instructional YouTube videos that outline the process.
Depending on where you live, there may also be a local shop that can do it. Might be best to call them first to make sure they can do repairs on HTC. I know that Batteries Plus performs HTC screen repairs if they are local to you.
Good Luck!