In a worst case scenario, the car will need new door and new rear quarter panel. Then they'll be various trim bits (there always are). The best estimate is 'several thousands'. Then, there may be further hidden damage underneath the car or to the wheel rim or rear suspension.
If you have to claim on your own insurer, then obviously opt for the best repair possible, including new parts etc. You can even insist on an MB-approved body shop instead of accepting the insurers offer to use their own repair centre (though there may be a small fee to pay for using your own repairer).
If aiming to repair it at you own cost, have a reputable body shop check it out, it may be possible to affect a repair without replacing body panels. Panel beating is highly skilled work, which is why most of the big doby shops prefer to just replace the entire panel. But it will work out cheaper if the damage can be repaired without replacing panels.