Google z4root. Its a free one-click rooting solution. You also must have Koush DroidX Recovery Bootstrap. Its in the market. Then you need to find a Rom and install it with the Recovery.
Make sure he is on the most current VZW software. Go to about screen and verify under System version; Version.2.3.340.MB810.
Once thats done, open z4root, click the permanent root. It will take a long time, sometimes it takes two times doing this, or may not "Stick" the first time. Once it is rooted you should have a superuser and a terminal emulator app in the app drawer. Then go to the DroidX Recovery Bootstrap. Click on the "Bootstrap Recovery" and reboot phone from the app. After turning off it will boot into the Recovery screen which allows you to load .zip onto the phone, backup/restore, and many other advanced settings. This is where you navigate to the ROM that you want using the VOLUME key for up/down and the CAMERA button for your selections.
Before you make ANY changes ensure you make a backup first, then wipe date/cache prior to installing your ROM. Then install ROM, all done from the Recovery screen.