Is it pretty easy to have an auto glass place remove my windshield and redo the seal?

Are you prepared to repair any rust or rot you might find in the pinch weld area? Most professional glass installers wont install a windshield into a rusty or rotten frame as they can't guarantee it wont leak. If your replacing the seal anyway go ahead and just cut the glass out with a razor knife and save the 100 bucks the glass co is going to charge.