The absolute most reliable Glock is a stock configuration. It will handle the largest variety of ammo consistently using the factory parts.
Knowing that, my recommendation is skip the tungsten guide rod and stay with the factory guide rod. Those modifications are for gaming guns anyways. For self defense, keep it stock.
Go with whatever sights you like, the Glock night sights are a great deal you might want to consider. The magwell wonít change any core function so thatís not an issue if you can find one for the Gen4 21.
Thereís absolutely nothing you need to do to the polymer. As long as you donít set it on fire or dunk it in acid it will last forever. Unlike the 1911 and any older gun, Glocks require very little maintenance - brush the dirt off and just a few drops of oil to keep it running forever.
The most important thing you can do is change the springs regularly. Springs keep the gun functioning and protect it from physical damage. Glock keeps the prices low as well so thereís never an excuse to not keep them fresh.
Being new to Glocks, the trigger is a much longer pull than a 1911. Itís a completely different mechanism so plan on lots of practice to eliminate the low left shots that are common for those shooting Glocks for the first time. Again, stick with a stock setup and master it.
This is a great group to ask questions of.
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