A few key points with drum brakes. The first is getting the drums off. This might be one of your biggest hurdles. I start by hitting the center of the drum between the studs to knock it loose. This often gets me where I need to be. However, if I have a lot of trouble, I employ other methods. Some brake drums have provisions to insert bolts to help you remove the drums easier. You just need the correct size bolt. Once you have the bolts, insert them into the holes in the front of the drum and run them down. This causes the drum to pop off the hub and come off. It's sort of like using a reverse puller. Here's a video.
Another issue you might run into is a rust ridge on the inside of the brake drum.
This ridge extends past the brake shoes; this can make removing the brake drums very difficult. In order to get around this, you need to loosen the self adjuster for the brake shoes. Most drum brakes have provisions to access the self adjuster for the brake shoes. You often need to remove a rubber plug in the drum or the backing plate to gain access.
You need to turn it in the opposite direction it normally travels in order to contract the shoes enough to remove the brake drum. This can be a real pain, but it's the best way to deal with this issue.
However, if you find that either you don't have access to the adjuster or the adjuster is stuck, you have other options. When confronted with this, I cut the heads off of the nail heads for the brake shoe hold-downs on the back of the backing plate. If you grind the tips of these hold-downs off, you can release the brake shoes from the backing plate. You'll be able to remove the drum, but it will probably come off as a pile of parts when you do this. I hope to make a video on this at some point. For now, refer to the brake shoe replacement video to see where the nails are located.
One other method to remove a stubborn drum is to use a special drum puller. You might be able to rent one of these from your local auto parts store. You install the tool and crank it down, and the drum should come off.Click here for the link to the Drum Puller.
One last thing on the rust ridge: If you're just replacing the shoes and not machining or replacing the brake drum, I'd recommend grinding off the rust ridge on the drum before installing it back on the vehicle. This will make it much easier to install the drum and adjust the brakes.