The conversion process is described here.
It does require a bit of work but so far people have had a fairly easy experience, and once you have done one, the others will be even easier. That said if you have some very special customization of the layout, it may require a bit of rethinking to use the new layout feature of Xtreme instead of complicated custom CSS.
As for any mental leap, I would not be concerned, the logic in Xtreme is the same as in Weaver II, things are just more rational and you have more options, but if anything, options are easier to find.
But ultimately given Weaver II pro is end of life, it is only a matter of time before you have to upgrade to Xtreme, so I would stay the sooner you get use to it the better 🙂