Hello!
Philo - sure thing, for a first paper model this is really something. I know I didn't get this far with my first paper model - boy, was that a long time ago, thirty years!
Then again, I'd like to tell you - paper models DON't really need wooden reinforcements. At least around herethey are designed around cardboard bulkheads and spars. If you get yourself some nice, consistent, 1mm thick cardboard, that's all you need. If it's supposed to be extra strong (seldom needed), you can always soak it with thin CA. You could for example glue two layers of stuff that plastic model boxes are made of, and you would be good to go.
TB - as for the leading edges - no, you don't really need balsa there. Even a complex leading edge, like that of a Spitfire can be made out of paper with just a couple of cardboard ribs beneath. The secret here is to shape the paper carefully before glueing, so taht it has the necessary curve on its own. This is done for example by pulling the piece of wing skin over some kind of edge, like the edge of the table top, or rolling it around a pin of the right diameter. You could also try some extruding - laying the paper part on a lyer of hard rubber and pressing it with a steel ball or something like this - it's good for wingtips, teardrop-shaped housings, propeller spinners and stuff.
Anyhow - good luck with your modelling projects and have a nice day
Paweł