PCV valve and starter question

Hi, this will be my first post to the forum I have appreciated all the info from other threads. I've got a 67 coupe with a 289, C-4, Hedman headers, Edelbrock(carb, intake manifold and cam). Just about finished with a total engine rebuild, repainted the engine well, replaced all steering components and all front suspension parts. My first question is, how important is the PCV valve? Is there a problem with just putting a small filter cap in it's place? Does it make a mess that way or change the performance in any way? My second question is, I bought a Ford racing mini hi-torque starter. If I'm reading the directions correctly, it says to hook up the large wire from the starter to the post nearest the shock tower on the starter relay along with the battery starter cable. And the small black wire gets hooked to the post nearest the battery. Does this sound right? My notes said I took the battery + cable off of the side closest to the battery when I was using a OEM starter.
Any help would be appreciated.

Thanks 66HertzClone. I ask the question regarding the PCV valve because I just put a set of new valve covers on and they have the large twist on type holes. The valve covers are the aluminum covers that say 'Mustang - Powered by Ford' made by Ford Racing. They came with a push-on type cap. Included in the package was a rubber grommet that doesn't even come close to fitting in the valve hole, but they included another grommet in the box that just barely covers the hole in the valve cover and fits the cap. My big problem has been trying to figure out what to do with the other valve covers hole since its a twist on type hole. I have had three different grommets sent to me, but none of them have a large enough O.D. to fill the hole. Wandering if it was a good idea to just put a breather cap on, but you answered that question. Ideally I would like to just have the grommet with a PCV valve in it.