1) Any and all "RUUs" will wipe your phone. 2) Any and all "OTAs" will not.
If you are having issues obtaining the official OTA via the phone's "check for updates" selection, I'd try a battery pull/sim pull, reinsert and restart and try again. If you keep getting a "disappearing act" after you "check for updates" I'd next try a factory reset and try again. If you still get the "disappearing act" I'd take it in to VZW and exchange it. You should at least be getting a "service not available" message or a "no update available" message. Either way you should not be getting a disappearing menu.
Note: This "disappearing" issue is totally different than the "service not available" issue. The "service not available issue" is almost always temporary due to the server connection, or temporary server issues, not the phone.
Edit: Okay, I just read that someone who was getting the dreaded "disappearing act" was finally auto-prompted to update, and it succeeded. So... I dunno.... I guess you should hang in there a while and see what pops up...