It's just a number. What possible difference could it really make to you? It's true that MEID was created to replace the ESN, an 11 digit decimal number with an eight digit hexadecimal (alphanumeric) equivalent, because the ESN was being exhausted by the wireless industry, not just VZW. The MEID is a 14 digit hexadecimal that looks something like A000000123CD456
To find out your 8330's ESN or MEID, from the Blackberry Home Screen select Options > Status. Or, just take the battery out of the phone and on the back of the phone you'll find it also.
If I decide to update the OS I want to make sure I'm using the correct one.
Huh? How are you updating the OS? If you're on BIS (Blackberry Internet Services), just use Blackberry Desktop Manager software, it should have come with your phone on a CD, to update the OS. Some OS updates can be done over the air (OTA): from the BB Home Screen select Options > Advanced Options > Wireless Update. You can also update the OS at http://na.blackberry.com/eng/update/
If you're on BES (Blackberry Enterprise Server), check with your IT department for updates.