Bin dar, dun dat! However mine was leaking at the main flange. The new technology rubber gasket just didn't work out. After I fixed it, I tossed the fancy robber gasket in favour of the tried and proven wax ring.
I really like what I see for floor boards in your 30 year old house. You don't see them built like that very often. My house was built in 1968 (45 years) and even it isn't built like that. All plywood.
Good luck with the repair.....shouldn't take you too long.