There's a 99% chance that the Max wheels won't fit on your 4500 lb. SUV. The Pathfinder has 6 lugs spaced at 5.5" apart (6-5.5" wheel), and wheel sizes range from 15x6.5 to 16x7, depending on what year and model you got. As mentioned in an earlier post, the wheel offset (how much the wheel sticks out past the lug nuts) is positive (meaning that the lugs are closer to the outboard side of the wheel rather than the inboard side).
I dont know much about the Maxima wheel you saw, but I bet its probably a 5-lug wheel (which means it wont fit a 6-lug hub) and a different offset. I havent seen any passenger cars that have 6-lug wheels.
Maybe you can find a wheel from American Racing, Eagle Alloy, etc. (visit http://www.tirerack.com>) that looks like the Max's wheel.