Not knowing just what got melted, it would seem that you caught it very quickly and, as a result, prevented any real damage. Good on you.
80 lbs, even cold, seems high but not impossible. Since you got to do an
oil change anyway, tell 'em to refill with 10W-30 and see what you get then. Remember, it's a new motor so heavy (i.e., 30 wt.)
oil is not necessary.
Yes, if I wanted the car, I wouldn't be troubled by this event.
BTW, I had the plastic
oil gauge line split on my car when it had less than an hour's running time on it - hadn't been on the road yet. BIG ball of flame out of the (open) engine compartment......testicles retracted to somewhere around my heart.....no damage whatsoever. Braided steel followed immediately.