You would send the FLA file to the collaborator. In most collabs you are required to send the FLA and the SWF via Private Message (:
Also on note about the whole "RHG has to be flash" subject, the whole thing is false. You can animate your RHG in any program, but you will most likely be at a disadvantage against other flash animators if you are using a different program.
Also to answer the 'skill level' question. Anyone can make an RHG but I highly advise that you get familiar with animating before you do so.
*Edit: Am I aloud to answer these?