Dents... apply a bit of water then go over it gently with a steam iron. This lifts a lot of the dent out. The heat expands the water inside the wood and "fluffs" it back out. (works on minor furniture dings too. )

The cracked area... you want to glue back togehter as best you can, then mix up a filler putty. OR just cut oput the dmaged area and replace more sheeting. Since you are already patching the sheeting in the wng bay beside the cracked area, I would go ahead and just replace a larger section.

The best filler is a mix of "microballoons" and epoxy. for a small batch, you mix the epoxy and then add the microballoons to make a filler about the consistency of common white toothpaste. (Crest is a good example) Thies wuill still be "damp" enough to stick to the wood, but won't be excessively heavy. The stuff is not too hard to sand when it sets up. (use 30 min or longer cure time epoxy... you nee the time to mix in the microballoons.)

You can make a filler by mixing the dust from sanding balsa with 50% yellow glue and 50% water to get the desired consitency. This stuff is not as easy to work with... but its very inexpensive. Note you often have to paint the area that this putty will be applied to with glue-water mix to get it to stick.

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Microballoons are available at most places youcan get model aircraft stuff. They are very tiny hollow spheres made of some kind of plastic. the stuff is mostly air really due to how thin the shells of the little balls are. (under a magnifyng glass... they look somewhat like the toy balls that kids jump into a pit full of at some Pizza places and pre-schools.)