The 19C barrel will not just drop in and be good to go. The outer diameter of the barrels are different.
Lone Wolf sells a ported barrel that converts from .40 to 9mm, but the port slots will not line up with the slide if you get the standard length. You would need to buy the extended ported conversion barrel that places the ports out beyond the end of the slide.
If you wanted a 19C as well, you would need to buy a 19C slide assembly for your frame.
A new magazine will be needed as well.
Now, you can buy a 9mm conversion barrel that is non-ported easily and just have a standard 19. You will only need the barrel and magazines for that swap. It is highly recommended that you get at least 500 rounds through a conversion before considering carrying it that way.
I have a 23C as my every day gun, and I have 9mm and .357sig barrels for it.