Lemme get this straight. We have to go to the members area, download the entire vBulletin 3.7.5 script, overwrite the current files, and then run an update script? This is the impression I'm getting.
To be honest, this is rather ridiculous. Coming from SMF, I can say that there are way better ways of doing this (Hell, updating from 1.1.6 to 1.1.7 was about 2 clicks in the ACP)... I'd say that install, transfer, and updating is vBulletin's greatest faults... And to be honest, I'd rather not have my forum offline for the time it takes to update all this!