How bad is it damaged? You could shop around and see if you can find a shop willing to fix the quarter panel, instead of replacing it. If more than half of the quarter panel is damaged, you will not be able to find someone to fix it. It probably is not worth trying to buy the salvage. Find out if they figured a new quarter panel or a recycled one. You may be able to save some money using recycled or non oem parts. Most people do not want to use non OEM parts, but I had a body shop owner tell me once that they prefer OEM because they make more money off of it, but that OEM parts are really not any better than the non OEM - when the shops get their OEM parts, they get the ones the MFG did not want to use. Those were his words, not sure if that is the case most of the time or if he had just gotten a few junk OEM parts and was venting.
Just want to add, in case this becomes a debate of OEM vs NON OEM, I had plenty of shops tell me the non OEM parts they would get would not fit. This shop owner told me he gets both that don't fit - OEM and non OEM.
Anyway - just some options to check on when you look over the estimate.