I have trouble starting

First you have to clarify the symptoms. "Doesn't start" can mean a dozen different things. If it was as simple as "buying a part" based on symptoms, we wouldn't need mechanics to diagnose them. Even the parts you mentioned indicate problems in two entirely different circuits so as a guess, I'm going to suggest the starter doesn't crank the engine. If that is right there is no need to be thinking about the ignition system. It's not even in the picture yet. One common problem on Fords is the heavy cable going to the starter has multiple strands of wire corroded away under the insulation. There is even a foot note to that effect in most replacement starter catalogs.