Truthfully I don't care about loosing root. Other reports say it can be re-rooted and the only reason I rooted was to get teh 2.3.15 rom leak from Motorola, which does have the update capability (just keeps telling me i'm up to date if I check though).
If I brick I do have SBF setup @ home to get it going, but yeah I would hate to do that a second time ... lol.
Ahh, if you don't mind SBF'ing then fine...
Rename Blur.zip to Update.zip and put it in the root of your SD card (make sure it isn't update.zip.zip).
Power off the phone.
Open the keyboard and hold down the "x" key. With the x key held power on the phone. Wait for the yeild sign. Release the X key.
Press the search key on the keyboard. On the menu that appears scroll (use the arrows) to Apply sdcard:update.zip and wait. When completed select reboot system now.
That "should" be it