I have yet to find the inspiration to write an automatic upgrade routine, my need for food and shelter keeps to coming up, but a manual upgrade is possible, I have done a few for clients.

If you are familiar with MySQL you should be able to create the new tables and alter the existing ones by reviewing the sql files in the /docs directory, using PHPMyAdmin will allow you alter and create tables

Typically a customized theme only requires the stylesheet and custom graphics
be copied to the new theme directory.

and of course back everything up before trying an upgrade.

I am of course available for hire to perform upgrades, and every one I do gets me that much closer to putting together an automated upgrade routine.