Easiest way to get it done would be to get the prior owner to help with either an explanation or hands on assistance. If that's not possible, try the Columbia
mail list on yahoo and this Columbia discussion board:
Columbia - SailNet Community
If none of that gets you the answer, and you can't figure it out yourself, consider the possibility that the part or parts
you need might be lost
, which might explain why the boom is not attached to the mast
A rigger could certainly help you, but you'd probably have to pay for them to assist you, unless you have them coming to the boat for another reason and you just casually ask them to help with this while they are aboard.