If you have standard nav, you have to download the updates to your nav data SD card - you can do it yourself.
If you have navpro, you can either do it using a SD card with downloaded maps on it to update the car's SSD map data or you can update via carnet online... I suggest that if you use carnet then you connect to like your home wifi and not use your phone data allowance- the full european map set is about a 6.5gb download!
In either case, no you don't need a dealer to do it, if you do, then you will pay!