this seems kinda simple to me....
#1. it would be extrememly helpful to know the original click tempo... this eliminates any guess work.
#2. set nuendo's tempo to original click tempo.
#3. zoom all the way in looking at the click track and cut or put a snap marker right at the first click... on the click track file itself... in the project window.
#4. select all the tracks in the whole project.
#5. turn snap on and move them all together so that bar 1 beat 1 of the click lines up to bar 1 beat 1 of the grid...(or bar X beat X).
now you have your whole project lined up to the click and the grid.
quantize to the grid until the cows come home!