In typical speedy fashion, the official Gingerbread update for the Motorola Droid X has already been rooted and mirrored for mass consumption. Two versions are available, as is usual for releases of this nature: odexed and deodexed. The instructions aren't exactly simple, and you have to know what ROM and version you're currently running in order to properly update (then again, chances are that if you're rooted and ROMed in the first place, you probably already know those details).
To download, head on over to MyDroidWorld and follow the steps appropriate for you. As always, be careful and make sure you're following the proper instructions before flashing, lest you end up with an expensive paperweight.