It not REALLY big but you will def be able to see from a good distance away. There IS a cable that runs from the antenna base to the head unit. It's about half the size (in diameter) of a television cable. I run through the hatch seal and place the base just forward of the hatch when I run it.
I put a good coat of wax down on the car prior to setting the mag base up there. Just rub it on, let it haze, and leave it there. Wipe if off when you remove the base.
You'll also need an SWR meter to tune the antenna once you install it. It makes a HUGE difference in range. You can either buy one (they're not very expensive) or you can borrow mine if you promise to return it. I think they're like $30. If you have a CB shop nearby and buy the radio and antenna from them, they'll usually tune it for you for free. It's always best to talk with a CB shop if you can before buying. They can tell you which models are easy to modify for more power. 15W is about as much as you'll want to go. After that, the signal to noise ratio starts becoming counter-productive.
Some of the El-cheapo Uniden CB units you'd find at places like Wallymart are actually great units! Good quality electronics, low noise, and easily modified. They just don't have all the bells and whistles that a $200+ unit might have but perform just as well.
This is also a great unit...
This is what I have in my Suburban. This one is modified for 11-12Watts. All of the electronics are inside the handset. There's only one small metal box that the antenna plugs into that you can install behind center console and out of site. Noce clean isntall.