I just rebuilt my single reservoir drum brake master cylinder a couple of days ago. It was pretty easy. It took me about an hour and a half start to finish. Im assuming you have a dual master cylinder. Im not sure how much more work would be involved in one of those. The only problem I had was that one of the seals in the kit didn't seem to fit correctly, so I ended up re-using the original since it was still in good shape.
You will save money by rebuilding, but it will take time and patience. I saved about $50, but I had to buy a brake hone for about $12.