Yes, one MUST do their homework to determine a value! "Most" insurance companies will pay out approximately 70% of the value of the vehicle, the repairs to the vehicle do NOT include any rental car cost. Also, diminished value is based on the amount of damage, the mileage at the time of loss. You do NOT have to accept aftermarket parts! Tell them you bought a Ram, and you want Ram parts! If the AM/KT parts do not fit like the OEM, point that out to the shop, and refuse to accept the repairs. "MOST" of either the shops or dealers will price/profit match the am/kt parts, ask the shop, and let them know if the am/kt parts do not fit perfectly, you will refuse the repair until it is right.
I proved that the am/kt doesn't fit like OEM to the lizard company, went through 4 fenders and we could get it to line up with either the hood or the door, but not both! The supplier brought another fender with him, (number 3) and when it didn't fit he said, "OEM doesn't fit any better" I then handed my guy an OEM fender, and in about 10 minutes told us, "ready for paint" Only had to show an invoice for an OEM part after that! LOL
YOUR vehicle, YOUR call! if it's not right, don't accept it!
The diminished value should be through the other carrier, not yours!