Swapping the dizzy is easy.

Rotate the engine so that the tdc mark on the crank pulley is pointed at the tdc mark on the timing cover. To be sure you on tdc for #1 cylinder, remove the #1 spark plug and feel for increasing pressure as you approach tdc with the crank pulley. Mark the location of the dizzy bolt on the slot in the dizzy body. Remove the dizzy cap and confirm that the dizzy is pointed at #1 on the inside of the cap. BEWARE! Note that the studs inside the cap may not go straight up to the plug wire connector on the cap. Trace the bump from the stud to the plug wire connector. If all is good, mark on the dizzy body where the rotor is pointing, remove the dizzy hold down bolt and slowly pull the dizzy upward, noting that the rotor will rotate as the dizzy body moves upward. When it stops rotating, mark that position too on the dizzy body (do not use a pencil for these marks - pencil lead is a conductor...). Now stab the new dizzy in place, aligning the rotor with the second mark you made above. WHen socked all the way in, the rotor should point at the first mark. If not, pull it and try again until the rotor aligns right. Replace the cap, align the new dizzy to match the marks on the old one at the hold down bolt (this step gets the timing close enough to crank), and try to start the motor again, testing for spark at a plug or the coil wire.