Bottesford,
database isn't used, config file you have to change.
At the moment the component complains if gallery2 isn't installed in this manner:
/mambo/gallery2
it only shows a warning you can ignore it, i'm programming the component to do better next version ;)
i think you have to adjust the userfuncs.php for your setup, because i forget to put in a change in the last relaise, sorry for that, but he gallery2 and the components are still beta.
you have to adjust the "config" function where a extra path is set and itemid is added.
good luck,
Michiel