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Just search around using Google, YouTube, etc. XDA is often a good source of guides and procedures for such repairs. Replacing the touch screen is a fairly common repair on smartphones. Not too bad of a repair, if you are handy with such things (from what I hear anyway, I've never done it myself). Getting the phone apart, in such a way that doesn't damage the casing, or any internal components is the biggest crux.
You will also need to determine if you need to replace the actual screen, digitizer, or both, as it can be the difference of $12 versus $50. Which of course is still much better than the $150 or so that HTC will charge you. I'd also buy one of the sets of tools for taking phones apart (around $10).