^ I don't remember anymore how I moved contacts but it wasn't hard.

I used the N900 briefly as my main device before switching to the XA2/SFOS.

Go to N900 calendar => Settings => Edit calendars => tap on Calendar => Export
will create an .ICS file (not tested).
IIRC you can tap on .ICS files in SFOS and they will get imported into the current default Calendar.
(SFOS has many such features that aren't selectable, labeled or documented, but simply happen when you "do the obvious thing".)

That said, I have long stopped using local calendars - CalDAV and CardDAV it is for me, all the way. I need the sync with my desktop, email client etc.