How do I replace the driver's window in my 1998 Nissan truck?

Take off the door panel. The window will be attached at two points to the regulator (the mechanical lifting device). (I don't specifically know about the Frontier without looking at it, but most applications are similar.) Anyway, roll down the window to where you can access those two bolts and unbolt what's left of the window. Remove the old window. Don't forget to run a screwdriver down the tracks to clean out any glass stuck in the tracks. Slide the new window down into the track from the window opening. You may have to angle the window down to get it to start. Don't drop the glass! Bolt the new window to the window regulator. Don't forget to vacuum out the broken glass from bottom of the door. P.S. The job is easier with two people.