I am confused. You want to replace the Expedition engine with a 6.0 Powerstroke?
First, the Expedition has a 1/2 ton frame while the Powerstroke likely comes from a truck with 3/4 frame, so it look like you have it backwards.
Second, you are replacing the Expy engine with a heavier one which will likely require upgrading the front end. Also, you are moving from gas to diesel which mean all the electronics will need to be transferred as well.
Unless you are very knowledgeable and have the proper facility to do the work yourself, the cost would be prohibitively expensive.
FWIW, the early 6.0 Powerstroke engines are considered lemons and you have to go through an expensive ($5K) process called bullet proofing in order to have it work reliably.
In short, you are looking at $5k-$10K to do the modification and you end up with first generation Expedition that is still worth, at best, only a couple of thousand dollars even with the modifications. You are much...and I mean MUCH better off selling the Expedition and getting a comparable Excursion. Just my opinion.