If you were here in Australia you would need to go through your own insurance company. If the driver of a car at fault in a crash car is guilty of a crime - i.e. drunk or drugged driving then his insurance will be null and void. I don't know how it will be in the U.S.

I would definitely let your insurance company handle everything. You don't want to get messed around in this, especially since a crime is involved. It maybe messy enough, you needing to do police statements and go to court etc. - A huge amount of precious time involved in this.

Always a bummer to see a great car like a W140 especially a flagship 600 go down like this.