Upgrade to phpBB3?

Well as people may know the current board is phpBB(Version 2), I know people have been shooting around the idea to upgrade to the newest version of phpBB(Version 3). Yesterday I dove in to the matter a little bit and it seems like its going to be a bit of work. I am willing to go ahead in the process to keep testing with an older backup of the database to see what the issues are going to be. Currently as you can imagine, the database is very large. This has set one flag so far being that the forums will have to be shut down for a period of time since I am not going to be able to run it live. Which means I will have to close the forums, download the database, install it locally, convert it, re-upload it, load the newly converted database into the newest version of phpBB(3). This process may take an entire day... or longer. Which leaves us with 2 options, close the forums for a day or play time machine and just load the database with the most current backup and lose a day on the conversion to phpBB(3). If anyone has a better solution that they have had actually work I would love to hear it.

Also if we have any skinners in the community I'd love to see a contest for best Brickfilms phpBB3 Skin.

Thanks in advance