I had to replace one of my entry door locks as well, due to a "stuck" lock. If I remember correctly, in addition to the four screws, there are two more screws on the striker plate (edge) of the door as well that must be removed in order to remove the entire assembly. If you can remove the inside plate of the latch assembly while it is still in place, you will be able to manually manipulate both the latch bolt and deadbolt enough to remove the lock assembly from the door. Good Luck.
P.S. Our unit is 2010 8315BSS and dealer gave us a replacement lock unit under warranty - no problem. Just had to return the defective lock to them after replacement was installed.