Great, so I'll assume your saying that it IS the switch, not the sending unit.
Switch found cheaply here:
http://www.rockauto.com/catalog/moreinfo.php?pk=939266
$11
Goodyear wants $90 to replace.
Wow
Lots of them seem available here:
http://www.carpartswholesale.com/parts/nissan/pathfinder/oil ...