1. It's not difficult at all, when installing you simply indicate which software you are using for your forums (and any configuration items, like forum database if different from the gallery, cookie prefixes, etc).
2. vBulletin has a deeper integration than the phpBB one and neither is complicated. If you had a choice, I would suggest vBulletin's.
3. The Admin Demo is offline right now after some upgrades, but we will try to get it back online soon.
Please do not PM me for support or sales questions. Thank you for your understanding.