Hi,
You could go down that route, but it isn't all that neceersary.
Max 9.1 supports importing fbx's onto the biped directly. So there is no need to use csm's at all. But you would need to use motionbuilder to convert your c3d's to fbx's.
You can import all the c3d's you want into motionbuilder, and retarget them onto your control rig (which should have origionated from your max scene using the character that you wish to import your data onto) and plot onto your max biped skeleton.
Once you are happy with your data and its all plotted down onto the skeleton, export the fbx's (this way you an batch out all the takes individually), and import them onto your max biped.
I wouldn't mess around with csm's unless I had to, its a crappy way of getting the data out.
Si