At the shop, I always dreaded 'comebacks'.
My first fix there many years ago resulted in a comeback, and never since. This results in a different approach, a different mental mind set.
As s side note, if a customer says "I'm going to sell it, just get it fixed as cheaply as possible.", you can be sure the car will be owned/showing up for at least 2 years or more.
What I often wish I could do over again are things I say. Better ideas and phrasing often comes afterwards.