How can I unroot a Droid Incredible with Unrevoked Forever to CyanogenMod?
You've got to do 2 things:
First, download the S-ON tool from unrevoked's site and run it according to the instructions. The main thing to keep on top of is the radio compatibility, particularly if you've flashed any of the Evo's radios to your Incredible.
Once you're back to S-ON, flash the latest RUU. Right now, it's 4.08.605.2. This will replace the ROM & recovery with stock versions. Be careful doing this, last I heard there's no way to permanently root the Incredible and regain S-ON after you've flashed a stock Gingerbread ROM. If you would like to re-root in the future, at least keep S-OFF.