OK -- after spending an hour searching the forums for more on this and finding nothing -- I looked at the code in the upgrade.php and it would appear that all of the scripts are in that -- and not individual files that one would upload as the upgrade document would leave you to believe -- is that true?
Since I'm at 2.0 and need to get to 2.5 -- it would appear that I will see a screen asking what version I'm running -- and I'll select 2.0. It then looks like it will then instruct me that it will run upgrades to 2.3, then 2.4, then 2.5, and finally the zipcode upgrade.
Is this correct -- do I upload all files but the config and Install to the server (will I need to change the CMOD of any files because of overwriting files?) and just run the upgrade.php as above -- or are there actually version scripts I need to find from somewhere?