If you only want one version installed then, IMHO, I would nuke the entire folder and install the version that you want to play. You will, otherwise, always have a mess on your hands.
Agreed with hansangb.
Don't try to deal with weapons, just learn to fly. Many years ago, with the A-10C, I spent weeks just learning to land it well. Don't try to be a warrior at the outset, just try to be a pilot.
It is the most expensive part of the package, so you must have been thinking 2500 to 3000 for a realistic total.
$2500 is my target for any new build, in recent years. That includes about $200 just for the PSU.