Picked up a used Hellcat Pro this morning, time to turn it into my primary carry weapon.  

Good deal

I have a brand new, never used IWB Bordertown Holsters holster for the Gen 5 Glock 19. It looked pretty close, so I shoved it in and it's workable. The last little fraction of an inch has a little resistance instead of locking in like their holsters usually do with the correct firearm. It's close enough, trigger guard is completely encapsulated and there's no protrusions that can play with the trigger.

I looked around and saw a sad and lonely Glock 43 magazine case, also from bordertown. I looked at the construction and realized it I could heat it up and reform it. 2 minutes with the hair dryer with the Hellcat magazine inside, and it's ready to go.

Apex trigger helps a bit.

This.  Apex trigger is an excellent upgrade.

How involved is the installation?  Are all factory safeties still intact?  

I took it out this morning and put around 50rds through it.  Nowhere as snappy as others have said, until I tried it weak hand only .  Apparently, I need to do that more often

So easy a caveman can do it. Couple of punches and a bench block or vice. Use of tape so you don't drop parts. Pretty quick job with multiple YouTube installation videos as a guide.

Trigger and springs or, just the springs?