if you can get the plugs out, take em out and get yourself a socket for the main pully, cant remember the size right now, think it was somewhere around 1 1/4 maybe or something close to that and try to turn the engine that way you should be able to see if the timing marks line up with the marks on the back cover, or with the marks on the belt if you can see them yet.

The tensioner is one of the items included with the TB kit from here -----> http://www.courtesyparts.com/nissan-timi...532_22_523&

If you find that its not toast, and are going to put it back togeher, make sure you get that kit, (or at least all of the parts shown) as they all should be changed while you are in there... plus the little water intake hose by the thermostat housing