The local 101 expert will no doubt be along shortly! Where are you, JW? 
As for the input levels, leslies are designed to be driven very hot, direct from the amp of an organ, 10-20 watts worth going in! So running a guitar into them with no amp in between is going to be pretty quiet.
Best of luck with the project. Although we love our organs and would prefer to see leslies used with them, we'd rather they were used musically than sent off to landfill or parted out.