My 0.02 cents
*Did this dealership put in the scratches - is this why they'll fix it for FREE?
*Will this friend of yours fix it for FREE?
I would give the dealership an honest chance & have the dealer fix the scratches for FREE as they mentioned.
Also, see if you can first talk to the detail person that is going to do the work on your car. Be very friendly and ask this person what they're going to do and... IMPORTANT --- "Point Out Your Concerns"!
If you're NOT satisfied with your conversation with the detail person then walk away(thank you) & take your car to your friend.
I you ARE satisfied with your conversation but later, you're NOT satisfied with the detailer's workmanship then again, take it to your friend.
I know this sounds like a lot of extra steps if things DON'T work out for you. However, this may in fact work out for you for FREE! ...insteading paying someone, even a friend.