I removed the strings ''I was replacing them anyway'' and used the tape/hinge method. Clean the surface under the old pickguard with something to make sure the new pickguard adheres well. Then simply place the pickguard where you want it and tape 1 side ''2 pieces of tape'' to create a hinge. Fold/lift up the pickguard and peel off the adhesive covering. Carefully drop the pickguard in place and press firmly. It looks great and is holding up well.
I found this method on Youtube. Google Martin pickguard replacement. I followed the one from Martin Guitars. Not too difficult, good luck!