Can I disconnect the Head Unit without issues?
 

I used to have an old audi and when I disconnected the head unit, I needed to find a password from the dealer to unlock it.

I just got a 2014 R8 and have the need to disconnect the MMI to swap the trim around it. Will it require a password from the dealer to unlock it after?

Not usually any more. The 'ol radio "key" doesn't exist any more. There is component protection so if you tried to replace the MMI with one from another car it will not work and gives the component protection fault that AFAIK can only be fixed at the dealer. But it might be best to get some other member's inputs first.