The Advantage sights are great and are quickly forming a large support group. You can check our choices of sights in Night Sight section or Target Sight section. I recommend you visit a few shooting competitions first like IDPA or USPSA and see what your fellow shooters are using.
The LWD-5406 is an SF style trigger housing that drops right into your G20 pistol. You can see it here http://www.lonewolfdist.com/Detail.a...&TERM=lwd-5406
at the bottom of this page you will see a list of items including connector, trigger spring and striker spring. These are the modifications you will want to explore. Installing them one at a time until you decide enough is enough.
Installing parts or working on your Glock is not a huge deal. Pick up a copy of The Complete Glock Reference Guide and tear into it! Unfortunately I am sold out right now. It may be a month or so before I have any more.
Changing up your recoil spring lets your tune the gun to your ammo. Many of our customers prefer the 20lb and 22 lb recoil springs on their G20 pistols