Just the hard parts start at $266 and go to $546 plus shipping from Rock Auto. I haven't figured why but they list different applications for the 2 wheel drive vs the 4 wheel drive/AWD.
To change to an OHV requires the tranny also. If yours is a 4WD/AWD you will need the transfer case too. Then you have to get around any electronics/wiring/computer issues. I have a 99 OHV Explorer that just needed a transfer case and I checked out what it would take to swap the engine in and it didn't take long to figure out that it wasn't worth the hassle.