Just based on the fact that the vehicle couldn't be driven away means that the seat needs to be replaced.
Britax does offer a crashed seat replacement program, if you qualify...I think the child had to be in the seat though. I'm not 100% sure on that....but you could always call
Britax and ask. You can even have them tell(or send a letter)
DH or whoever that the
Marathon does indeed need to be replaced.
When you turn the seat into the insurance company---cut the harness straps, and write all over the seat with a permanent marker. DO NOT USE, CRASHED SEAT, UNSAFE. Hopefully that will keep someone from thinking...ohh free
Marathon, I'll use it for my child. See if they'll let you have the cover, hugs and chest clip as spares. I know you got a
regent...but you could probably sell the cover.
You've done the right thing getting your daughter a new seat.
Susan