In article ,
micky wrote:

some stuff

I haven't piped in on this one because I don't know much about toilets,
either. But when did you decide that you had to pull the tank? I'd start
with something like this:

http://www.amazon.com/Fluidmaster-40...dp/B000BOCAB2/

which you can install in 10 minutes, and see whether it fixes the leak.
No need to figure out what old system or combination of systems is in
there now, these parts all work together.