I’m not a mechanic but I’ve replaced 3 engines in f-250s myself and also paid to have a k2500 engine swapped. You are probably looking at 2k to 5k. It really depends if everything is there and if anything else needs replaced or gets broken.
I know it won’t help but my father in law just put a v8 back in his suburban. Bought a rebuild from Chevy and we put it in. With my labor cuz he is my boss and one other guy he had about 3900 in it. Hope it helps and gives an idea
The plug issue ( their plugs get so carboned that they break when you try to change them). very common issue, google it. Also, the fuel mileage is a joke.