Perhaps a little more information might help someone decide whether to help you:
For what reasons do you want to convert from Gallery 2?
Will the G2 and Coppermine galleries need to co-exist until conversion is completed?
Will you need it to have the same visual appearance as the rest of the NANFA site?
Are there some other specific expectations that need explaining?
Sorry for the slow reply, for some reason I was not getting notifications... anyway to answer your questions.
Gallery 2 is no longer supported nor being updated and we are concerned about ongoing security. Plus there is no one to teach me more Gallery 2 stuff to continue to manage the site well. So I would rather up convert to Coppermine and learn more myself so that we could maintain going forward.
It would be preferred for the old site to stay live until the new site was up and running. But no need for them to "co-exist" for any period of time. We could even tolerate some short period of time (say a few weeks or a month) where both sites were down.
No, we do not need to maintain the visual appearance of the rest of the NANFA site. Managing he appearance would be something that I would hope that I would be able to learn to take care of myself. But regardless, it would be totally acceptable for the site to ahve a different appearance.
My only other expectation is to keep the current permissions and structure so that the photo owners still manage their own content. Also my other expectation is that I might get some opportunity to learn so that I could do more for myself in the future.