Sorry, to hear that happen to your car. It's always slad to see a nice car being damage. The good thing is the Mercedes bodyshop is one of the best in the area in Vancouver. I had a chance to tour it the other day and I have to say I am very impress.
Regarding your bumper, You do not have to worry too much about it because all the related components that are damage will all be replaced. The concern you should have si the rear quarter panel. Since it's a unibody car, Damage at the area like you describe, there might ne a chacne that they have replace the whole panel. In doing that, you might see welding mark at the joints which a shop like Mercedes will cover it up with body sealants. If done properly, you will neve notice that the car has been hit before. But if they do pull it out and straighten the panel, likely you will notice that the panel has been damage.
Regarding your dimension, they should measure the car to make sure it's straight so you will not have problem with fuel door not opening properly or not. Make sure when you pick up your car, check out the repair and try everything. Also check the gaps between all the opening, such as trunk, to the body. I believe your car is in good hands.