Good for you and good for him, so what. Proves nothing in my case. Of course I do not know everything, but I can pretty much tear down and rebuild every unknown to me engine and put it back together to run forever. Same with ATX and no formal training in it. I have rebuilt many, they all lasted for years. Those people in Detroit know no more than us and the knowledge is out there. An SPI or zetec is a tinker toy to me. You should try like a six cylinder motorcycle like I have. Far more parts.
Clearly your mech did not want to do extra stuff to do the swap, all mechanics are in it for the money. That means you do the easy work and avoid the troublesome stuff if you're smart. You should try it for awhile, lose enough money and you'll come around to why he was the way he was. Of course they have to lie to back it up. At our garage, we wouldn't lie, just say why we won't do it and then offer the swap but at high enough cost to generally drive them away anyway. Everybody has big ideas until the money figure shows up. One is not in business to give money away to others. Problem is, the public now expects you to or you are not giving them FULL service, the major reason I left the parts business.
I do 100% of my own work, have never paid a cent to have work done except maybe machine work. I could do that if had the equipment.