sure it can be fixed i have fixed much much worse.
#1 belt sand all soft edges at a 45 degree angle (dig deep) then belt sand all remaining swelling
#2 use straight edge like a yardstick ect to build a form to where the edges used to be aluminum furnace tape can help build your forms in extreme cases temporarily screw down wood forms
#3 i know many people will say to use wood hardener and i used to be one of them but i no longer use it. it can react primer , paint ,art and leaves the wood soft and spongy
#4 instead of wood hardener use fiberglass resin mixed with 10% acetone the wood sucks this stuff up like a sponge and when it cures it will be harder than original. let cure for 24 hours
#5 mix bondo with bondo brand fiberglass resin auto body guys call it rondo pour it into the forms you made
#6 use automotive glazing putty during the finishing sand it dries in like 5 minutes cover that whole damn cab with it its fills all the sanding scratches and sands super easy
#7 USE OIL BASED PAINT or better yet automotive paint and an hvlp. many local auto parts stores can computer match your paint and sell you a pressurized can for $10 2 cans will do the whole cab