$650 plus a couple of hundred to ship, so maybe closer to $1K?
Time and cost to unpick it, add any local repair, and you end up with a 40 year old panel back on the car.
I think it's borderline for me.
I get the impression you are doing the car up to a pretty high quality, and since you are paying for the repairs to be done, I'd prob go for new if you can handle the price difference. Maybe the PB can give you an idea in the time he'd allow for the repair vs replacement to help you decide?
I'm working in a lot lower value of end product than the RS, but I would have given it a go just cutting out and making a repair.
Someone with alot more skill would be able to do a decent repair I'd reckon.