Hi,
I replaced my fuel tank on a 90 2.5NAD about a year ago, it was a sod. I was told by the garage to "Wiggle it" !!, from memory fit left side first, then lift right hand side and between the 2 of us we managed it !!
This is probably not the answer you want !!, you probably need someone by the side of you that has done it and shows how they did it