I have a 2011 yeti with a bolero head unit but I want android auto or at least a map and a backup camera, I found a mk1 Columbus used and my question is if I can just swap them and type in some code or are they ECU linked? Is it possible that the Columbus unit is just a display and a computer is need in the glovebox as for newer Columbus models?

If I succeed swapping and making it work,  what do I need to do to have smart link?

The units are ECU linked so you will have to reprogram the ECU

As for Smart Link it's mostly dealer only at a cost now of £170+ However there are other places on eBay that do it cheaper.