[Sicklyscott]

I don't think this is grounds for a new car. Part of replacing the motor was probably undoing the axles etc. and chances are the caliper came off. They probably didn't tighten it to spec which cause the issue. I am by no means suggesting this is ok, just stating it's further proof of insufficient attention on the mechanic's part.

With that said and adding in 100k mile car into the mix I don't think there is any basis in Honda or the dealer in "buying the car back" as if it were a lemon or frequent warranty issues. The dealership however might be open to a decently higher trade-in value if they're interested in making things right with the customer.

In the end I do think a new engine hurts the value of a car. Failures do happen but so does abuse. With documentation that shows the failure point you might be able to persuade a private purchaser that there is no hit to the value of the car. Without that proof however I'd err on the side of caution and assume it was abuse (over revving, over heating, loss of oil, general abuse) and would figure the rest of the car was treated just as poorly (trans, suspension, brakes) and wouldn't want to touch it.