Bought a 2007 Nissan Frontier and the dealer didn't know whether it was an LE, SE or XE

There should be a badge on the tailgate. From the description it sounds like you have a SE. Unless you truck has the 4 spoke wheels then you would have a LE. But more than likely it is an SE. XE is the basic model, SE mid of the road, and LE top of the line.

The LE is luxury edition is probably what you have if it has the basics, the SE is the sport edition and the XE is the extream edition.

Basically the most frontiers that has that are the LE and XE