RE: balsa / plywood repair tools
Buy the usual Zona hobby saws, also known as razor saws, coping saw, #11 hobby knife( and buy the large qty of blades,100count), good aluminum or steel straight edges in 12" and 36", a square, aluminum 11" sanding bar and if your budget allows, a scroll saw or 9" band saw, hobbico/GP builders triangle set, contour sander. Other tools that are very usefull and never think of them till you need it is a mini planer and a balsa stripper, for making your own sticks out of sheet stock.