Nissan Repair Questions? Ask a Mechanic for Answers ASAP
There isn't really a way to get it in there wrong. Maybe someone used some silicone or gasket maker and essentially glued it to the block. You tried installing 8M bolts in the holes and pressing it out by alternately tightening the bolts? It should pull out fairly smoothly.
Can you send over a picture so I can see if anything looks out of place?
You probably already have this diagram, but just in case you don't: