The musty smell is from mold growing on your A/C evaporator coils. This happens because you turn off the A/C when it's cold and wet inside.
To dry the water out, just turn off the A/C by putting the selector in one of the vent positions, set the blower switch to high, and let the fan dry it for the last mile before you shut off the engine. Since you already have the smell, the mold-resistant coating in the condenser is worn out. DO NOT spray it with Chlorox, Fabreeze, or even that fancy A/C cleaner, anything will corrode the bare aluminum condenser coil. Basicly just remember to shut it off early every time you use it, forever. It is a good thing to do on all cars, and prevents the mold from ever occurring.
Put the blend motor back togather, it is not leaking, the water from your A/C evaporator above it is just dripping through it.