I think that if you are interested in theory, you should treat it as a separate subject and dig into that independent of your concertina playing. It's an interesting subject, but can get deep and irrelevant quickly, unless you are composing. Playing, a lot of the theory has been done for you already, and whether or not you understand what's going on can be relatively irrelevant, and as Late says above, you'll stumble into what you really do need to know. That said, understanding what lies beneath what you're doing definitely helps appreciating what you are doing. Some things are as clear as glass, but you don't appreciate them until they're pointed out.
I started concertina with a long background in music, and I started learning directly from written music. Now I am glad I did--it's opened some doors for me, both in terms of what I can do on my own now without having to hear things played first, and for playing opportunities, like the year or two I spend playing early music with a viol player, and quartets with some string players (both of which I never anticipated when I started concertina!)