Everything I'm spouting off, I learned from the Firestik web site. 2 weeks ago. I've never had a CB before, this is my first. My point being, it's not nearly as complex as it seems now. I was in the same boat as you seem to be, and was <this> close to having a shop install the kit for me.
Now, though, I just look back and laugh. Those were the days.
Ahem, anyway ...
So we're talking about two different grounds here. You're referring to the electrical ground, or the negative power lead for the CB, and you're correct. Red to the battery, black to a nice shiny bolt somewhere on the body or chassis or bracket or something near the CB's control box.
I'm referring to the RF ground for the antenna. If your antenna isn't grounded to the body or chassis or bracket or something near the mount, things no workie. Standing waves, RF reflectivity, smoking CB transmitters, blah blah.
Once you get all the cables hooked up, plug in your trusty SWR meter ($15 from Frys or Radio shack) and check your readings. See http://www.firestik.com/Tech_Docs/Setting_SWR.htm
for how and why. If you're in the red after many (many many many) attempts at tuning the antenna tip, you likely need to ground the antenna/mount. There are a ton of threads here about grounding. If you're in the red, do NOT transmit with your radio (see 'smoking' above).
As for the install kit, though, I think you're on the right track.