What would happen to the car if you opt to hand it back and walk away ( as I understand you can ) ?
Does it go into the MB Approved Used stock , or just go to auction ?
If the latter , it might be cheaper to hand it back , then go and buy it at the auction - bearing in mind how much you'd be prepared to bid .
They give it to BCA to auction off. This happened to my E250, they collect inspect and then BCA take control.