Glocks do just fine unmodified. I would suggest that you pass on the extended slide catch and mag release...you will find neither is needed. Use your weak hand to activate the locked slide and get the gun reloaded...this will work on all autopistols and is a good habit to get into. With the extended Glock catch on the smaller compacts, I have seen several that created problems when the shooters thumb would unintentionally activate it partway through a magazine due to recoil. Both the extended slide catch and the extended mag release are more likely to snag on clothing, etc. when carried CCW, precisely because they ARE extended, and I have seen that mag release button cause problems for shooters who...because of the longer button...no longer needed to shift their strong hand grip to push the button, creating a situation where the OTHER side of the catch that comes out and away from the frame, was blocked by their hand/grip.
I think a good set of tritium sights (night sights) is an excellent addition, and I personally like and use the Mercaldi Grip Decals on several of my Glocks because I like a rough grip texture for shooting, but the main thing you need for your new G30 is a good...really GOOD... belt and holster, (do not wimp out on the belt...very ijmportant!) and lots of good quality AMMO!
For sure, get a good small light like the SureFire E2e, C2 or similar (BrightFlashlightsand G&R Tactical here on the board are both great dealers and wonderful to deal with) and carry it as often as possible (remember, night sights cannot ID your target for you!)...you will NOT regret it!
Good shooting!