I am new to the world of firearms and having a Glock 21 as my first one. I have been looking online at several sites for aftermarket parts I just wanted to get yalls opinion on "upgrading" with aftermarket stuff because their are literally hundreds of thing you can buy. I am a tinkerer by nature I have to take stuff apart to see how it works my questions are. Sights are Glock sights bad? Barrels are the stainless steel needed? Guide rods do I need a steel one or a tungsten? Spring weight stiffer or lighter? Whats best? Should I mess with stuff in the slide? Firing pin little springs etc? Should I do anything to the trigger? Or should I just leave it alone?