There should be some maks on the dizzy. Fit the new one in as close a position as possible to the original and it will be ok. You could have the timing checked if you are worried about it.

Just pop the cap off with the leads still attached. Unclip the wiring. Undo the 2 bolts. Old one off and new one on. The dizzy drive will only go in the end of the cam one way.