As much as i know of there is no program that can edit 3do files. You can convert them into another extension using 3d object conventer and try to edit with various 3d editors. But you have to crack the program first cz it's not free. And also you can edit 3do files with Shstudio but you can only hide some of the parts that 3do extension includes. So thats not entirely editing but can be usefull sometimes.