You do not need to remove the blade gaurd to change the blade. You only need to raise it enough to acces the blade screw. Unplug the saw. Raise the blade arm. Raise the guard to it's upper position. On the left side of the blade, just forward and up slightly from the blade screw is a screw for the guard bracket. Loosen, but do not remove this screw. Once it's loosened the guard can be raised farther exposing the blade screw.
pg 6 of the manual illustrates this process, here's a link so you can see the parts I am discribing,
click the pdf icon next to instruction manual, then open the file.
As for the blade wrench, this should have come with the saw, there is a slot in the base for storing the wrench, on the back left side, it slides in and out for safe keeping. If you have misplaced the wrench the DEWALT part number 608563-1