I spent a large number of years as a bodyman, and I am here to tell you that MOST leaks arent from the windshield. If it leaks when you are parked... it aint the windshield. If you have the chrome off and spray it with water hose or try the air trick Blue Beast suggested and can see the water leak then yeah re-seal the windshield. Most leaks that are suspected being from windshield end up being rust in the cowl or a leak around the drip rail (above door) from old/cracked seam sealer. If it has a luggage rack on top, those leaks also run into the interior roof channels. Water that gets inside of the roof channels will eventually run forward when you hit the brake and run down the windshield post. This type of leak wont even get the headliner wet, and yet ends up on carpet.
I will be posting some photos of a nasty cowl leak that I repaired. The guy i bought the Bronco II from, said "oh and the windshield leaks a little"
Pfft... poor winshield got a bad rap.
B)