Selecting an A&P is more about the A&P's reputation than who's aircraft they've worked on.
I know several A&P/FBOs who would be able to show you all the work orders for the past several years/decades for the aircraft you are buying. when the guy who you select wouldn't have a clew.
Yep, and they may even provide you full disclosure on what they know the short comings are from the prior relationship with the plane. There are lots of times shops suggest work to owners to ake care of little things before they turn into big things. They cannot demand they be dealt with yet as there is no overt problem, but it's coming. Some owners decline.
Not everyone is a dishonest scammer, not even close really. The problem is they do exist with a great enough frequency it is a valid concern.