RE: NAV Integration with CRM Online
I would not consider this a "new" integration. As Marco said, you need to be on a CU that supports OAUTH--which I think all CU's published in the last 10-12 months do support. Once that is done, then you're just pausing the current integration, moving CRM data to CRM Online, and then re-connecting with OAUTH to the online db.
The only potential issue would be if in the move from on-prem to online, you made significant changes to the CRM data--particularly if the record id (GUID) changed.