I also am trying to find a module for adding additional signup fields if anybody would care to help me on that one as well...
Drupal comes with Profile. This supports configurable user profiles. I suggest you have a look at that first, before trying something else
Thoughts?
Thoughts enough 
... but what is it you would like to know? By putting it this way, it's not very clear to me (perhaps my fault)
Do you want to know if this can be done with Drupal/Ubercart? Yes it can.
Best,
VinceW