I'd burn one, two, or three with the plumbing buddy and pick his brain!
If yours is shot, make your life easy and just go with another tank with an insulation jacket. Like Pinky said, it will be at least 5 years till you see an ROI not to mention the maintenance.
I'd try flushing the old one to start if it isn't electrical. If it's been making random "popping" noises it full of sediment or maybe Pinky's rust/clog suggestion.
Good luck!