If you can get a digitizer that cheap and feel confident enough, I guess that may be the way to go. Either that, or if you have insurance on it, you could turn it in for a new one (under mine it would be $50). But if the screen has the troubles all the time like you just described you definetly need to do one or the other.
There is a post in here (I think it is stickied up top) that has diagrams + instructions on taking the Omnia apart!!
edit: My bad...not only isn't it stickied...it is the last thread on the last page!! Diesel posted it, if it helps, feel free to hit the thanks button

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http://forum.ppcgeeks.com/showthread.php?t=46644