While this isn't model-train electronics, the stuff he demonstrates is probably applicable to them in some way. Like his tagline says, "I hope you learned something".
Fixing laptops is probably harder than fixing model trains in many cases. I've worked on enough laptops to know that many are a PITA just to disassemble and reassemble, never mind the repair as well!
The problem selling a board to a non tech is if he destroys it, he has no way of having MTH replace it and you know he is coming after you. I made the huge mistake of selling a non tech a 5 volt board a few years back. He ruined it and came after me like gang busters for a refund.
Yep, I don't sell boards either as a rule. I did sell a 3V board set recently, and I sent the buyer a video of it running on the test set, and I made it crystal clear that it was a no-return sale! I never heard anything back, so I'm presuming he didn't toast it installing it.