Hybrid rebuild help

thanks for the reply im refering to the inside I pulled most he flaking off and theres just styrofoam there. It seems to be the same type of panels as the floor was made of maybe a 2 pieces of some type of 1/8" wood with 1 1/2" styrofoam sandwiched between the two pieces. I was afraid that the outside would be thin and glued to the panels. The floor and walls when wet were just deteriating so couldnt tell what that wood would have been. I was afraid that the outside would bubble and would not be unable to get it back smooth when attaching it to the new styrofoam causeing more of a problem than I already have. Ive read where people have just sprayed it with a bleech and water mixture but Ive been told that only works on smooth surfaces and it would be best to just replace anything that has gotten wet.