It would be best if you simply addTemplated a new object with the mesh onto the existing SA3 complex bundle. Make the SA3 invisible by using the ObjectTemplate.createInvisible command. (Only use it on the complex object that is added to the lodObject! Not the main PCO!).
If there is anything else visible like visible wing meshes, make those invisible as well.
Then addTemplate a new object that uses the camel mesh.
Sure you can simply replace the main mesh, but it will screw up the flight physics for the missile. So unless you know how of fix the wing positions and such, I'd recommend my method.
Also, you don't need to have collision physics for the new mesh. The now invisible SA3 missile hull should remain solid, so make sure the new object your addTemplating has collision physics turned off.