New guy here;

Getting into NRA High Power.  Wondering if a FAQ exist somewhere on fitting my rifle with match type sights.  

I.e., I've had it recommended to me that Anschutz or Redfield is a good front sight; and to seek out a Redfield International, Olympic, or Palma rear sight.  I've been to Champion's Choice in Lavergne, TN and looked at a Centra they had, as well as some others.

What baffles me, is the vast array of front sight inserts, as well as rear sight assemblies, and the various parts required to use them.  

In my eBay searches, I see some sights with a rear aperture, I'm wondering if these will take another manufacturer's "variable size" aperture (is this an Iris?); what is standardized with what, etc.

One fellow I shoot with had a good condition rear sight assembly with an aperture that you turn, and adjust the size of the hole (I think this is called an iris, but I don't know for sure).   His price on it seemed to be very fair when compared to eBay completed items (that is, I can't beat it anywhere) but I would like to know either manufacturers' resources or whether or not something exists, either here or elswhere, on what means what... like, what's the difference in a globe front sight vs. ??? else; what's a Palma rear sight, etc. etc. etc..

Will be waiting patiently for the mist to be cleared; all help is appreciated!

For this type of question, and others related to US NRA Highpower, you'll get a better response at NationalMatch.us.  There are a variety of front and rear sights in use, and what you choose depends on your needs.  You'll want to specify the rifle type (bolt gun, spacegun, Tubb 2000, etc.), whether you'll be shooting across-the-course exclusively or will also shoot Long Range, and whether you want to be able to mount a scope for any-sight matches and/or load development.

I would avoid Redfield rear sights as they're not as durable as modern sights.  The better rear sights are Warner, Centra, RPA, Zelenak and PNW.  Warner is considered the gold standard and priced to reflect it; however, I prefer the Centra.  The available front sights are too numerous to list, but you can reduce the options by specifying what you'll be using it for.  Most folks use a 22 mm front globe, although I prefer an 18 mm.  Ladder fronts are preferred so that only minor elevation corrections are made with the rear, thus maintaining a consistent head position and reducing wear on the rear.  Variable irises front and rear are very common, and models from Gehman, Anschutz and Centra are available.  Rear diopters are often used to get proper focus, especially if the necessary correction changes.  You'll also need front and rear mounts (they're sometimes incorporated in the sight) which will depent on the rifle.