ergophobe - 9:37 pm on Mar 4, 2013 (gmt 0)
You have a few options, but you will most likely want to use the Feeds or Migrate modules
That would be to get your content in there. As for the URLs, that would depend on how they are currently stored and how easily you could map them to the new system.
In any case, it's not likely to be a straightforward so keep good incremental backups as you work through issues so you can always back out to a known stable state.