SBFing erases everything on your phone! I used Titanium Backup to backup ALL my apps before I began. It just makes it easier to restore your phone to "like you like it" status afterwards.
I followed the instructions on this page to SBF back to stock 2.3.340 from ApeX 1.4.0:
Complete Droid X .sbf Flashing Guide
It has links to the files page here:
Droid X SBF
You will need Current SBF file (VRZ_MB810_2.3.34_1FF_01.zip)
(DO NOT USE Older SBF files!)
Windows Utility RSD Lite 4.9 (if you are using a Windows system to connect your phone)
The current Motorola USB drivers
Update your Motorola drivers 1st, then follow the first two instructions on the Flashing Guide:
Put phone in bootloader
Use RSD Lite 4.9 to SBF the phone
READ THE INSTRUCTIONS CAREFULLY! Don't miss any steps (like the SBF file has to be unzipped before it it used, etc)
It will take a few minutes (10 to 20) and it is finished when the phone reboots (READ THE INSTRUCTIONS)
My phone got stuck in a reboot loop, but as per the FAQ on the Flashing Guide page a factory reset fixed the issue.
Your phone is now just like it was out of the box (except it's got Froyo instead of Eclair). Setup the phone and enter your Google account. From here you should be able to check for updates and get the GB OTA update. If you do this, you will NOT have root until someone cracks it for GB. None of the current exploits work.
I followed this page to get GB with root:
Official DX Gingerbread 2.3.3 (4.5.596) Release Thread - Something for everyone
I used the 2 Part method (Patched update.zip (not signed))to get GB with root. 1st you root the phone with z4root while it's still on Froyo then use Droid2 Bootstrap (not DroidX Bootstrap) to install the two parts one after the other. Went like clockwork, and I've had no major issues since the manual update. Once again, READ THE INSTRUCTIONS!