MB vehicles leave the factory fully protected against weather attack. Nevertheless, how each individual deals with maintenance will determine how effective will the factory built defenses be.
Galvanized steel is prone to attack by chemicals (like street treatment salt and acid and grim rainwater), so it has to be protected by maintaining surfaces cleaned and if possible water resistant (like with waxes and sealants).
This general maintenance should be typical for any finish, since on non-galvanized steel surfaces the protection is just as good, by dipping the metal surfaces into proven corrosion resistant compounds.
Without taking care of your car, expect to have to pay the piper at some time, generally in the somehow distant future. Understand that Aluminum itself protects itself from corrosion with a clear or milky coat which forms over its surface with time. So everything requires cleaning and protection.
My advise is that instead of going jumping through hoops speculating how concerned you should be, get into a car care web store which post a maintenance manual, such as Autobarn, Autogeek, Car Care...
Cheers and enjoy the exercise of maintaining the car and the beauty of the MB ride.
PS Note that if you wish new primer or base paint to bond well, an electrostatic gun should be used to apply them, or the surface should be treated as recommended by the paint manufacturer prior to application. As for the clear coating, PPG European Formula Ceramic Clear Coat is the ticket (Superhard protection surfacing product used by MB). Don't allow shysters or discount paint outlets sell you a poor job.