My left side seal failed a month after my 4th anniversary. The drum was so locked I couldn't get it off or even drive the car, so I took it to Merv's Auto in Lorton, VA. I still had the left-over, single pair of brake shoes from the last failure, so they used that and did the the single-side job for me for $316, total.
They explained that it looked like I dented the center of the seal hammering it in with a poorly size-matched tool (I was never confident I had done it right).
Lesson learned for me: Use the right tool for the job, or leave it to the pros.