Just to re-affirm what Bugly and Aggie12 said, Steven helped guide me through upgrading my .340 (rooted) setup with the two P3Droid files (rooted, "method two").
We decided / deduced / guessed, after a little discussion, that the two files Blur_Version.2.3.340.MB810.Verizon.en.US-Part1.zip and Blur_Version.2.3.340.MB810.Verizon.en.US-Part2.zip were actually patch files that P3Droid must have built from the OTA. My guess is that the first file contains the bulk of the OTA patches since the sizes of these two files together (113 MBs) were less than either of the [de]odexed .zip files (163-ish MBs). I thought that this first file didn't involve adding the root components, but I found root and busybox references inside the .zip file. The second (part2) file was less enlightening.
I too did not do any wipes and the install went very smoothly.
Big thanks again to Steven for guiding me through this on my X. Good to see and experience D2 Bootstrap and ClockworkMod first hand and the differences and similarities to rooting my Eris and using Amon_RA's custom recovery.
Cheers!