if you decide that you are going to change the brakes anyway before taking the drums off, you can flood the drum with wd40, then release the brake adjuster as mentioned above,and then its simply a case of little bit at a time, working around the drum tapping opposite sides in turn .... do too much at one point all at once and you will lock the drum against the shoes, remember the shoes are quite wide. Turning the drum as you do it might help to push the shoes out of the way a little.
wait until you have to split the drum from the hub

that will either drop right out no problems or be stuck so tight you'll think some git welded them together
