Son cracked a piston, cost me $480 to get that diagnosed. Told whole engine needed to replace and not worth it. Van was a Florida car and body good. $3,600 from one shop, but blue book is only $1800, so it doesn't make sense. I work on cars somewhat, worth trying myself in the back yard?

 

Unfortunately, I don't have a working crystal ball, but maybe ask some questions that you have not covered yet.

Do you have the facilities to swap a replacement engine in good condition from a salvage yard?
Have you checked if there is one available?
Only you know the present condition of your vehicle, was the maintenance done to assure you the rest of the vehicle will not need any other extreme work ?
Do you have another vehicle to use while you tie up this one ?
Keeping in mind you want to get an engine as close to the same year , model and care as yours?
Sometimes it is cheaper, if all goes well and you do a good repair job as compared to buying another used vehicle you know very little about and could cost more in the long run.
I know you gave this one some thought,,,,,,,,,,,,,,,,,,,,the size of your bankroll ?
I know there are some other questions that maybe someone will bring up that have not been asked so far.

What if you were to open up the engine and replace only the necessary parts ?

 

If the A/C is strong, the tranny solid and the inside very nice ... in my book, well, that would tip it towards fixing it yourself, as a back yard mechanic.
However, if the inside is cracked or abused, I'd let it go.

look on it as a personal driver - do you want to drive it yourself?...