well as far as touching any modifications: the googlebase mod file names all begin with google so the mod files shouldn't touch any modifications of the cart itself.

Of course look at all the file names and use your own judgement.

Regarding the sql updates. If ever there is an uninstall sql, that is what I always go with. I uninstall and then install the newest sql.

The googlebase mod versions on my pc all have an uninstall file so check the files for the version you are using to see if you have an uninstall.sql.

And again use your own best judgement and always make a backup of your database and your store before you do anything.