Diminished Value on a 2007 BMW 335i?

A flatbed didn't secure his load and I ran into something that fell off and hit my 50K BMW. Repairs are thus far slightly over 6K. I'm collecting through their insurance. I have not brought up diminished value, but I will soon, what are my options in north carolina? Should I get an independent appraiser and if so, who is going to pay for it?