We could spend more time on antennas than radios, as there's frankly just as much to learn. My recommendation is get lots of them
and experiment, you'll probably get 2 or 3 before you decide on the "one."
The first thing you need to decide is what type of mount do you like: PL-259 or NMO. This is important since it dictates what types of antennas you can use, and can you swap them out freely. So when you look at antennas, note how it's one or the other. PL-259 is what your CB probably has, while NMO is a larger diameter, more like 1". Here is an NMO Cable:
Here is a typical PL-259 cable:
Mounting your antenna has lots of options as well- on your bumper, your fender, rear hatch, your roof... each one has its own +'s and -'s, so what to do depends on your situation. THEY ALL WORK. NO MATTER WHAT IT'S GOING TO BE WAY BETTER THAN YOUR CB. So don't sweat this too much. However, you'll come to learn that there are in fact performance differences with antenna locations. Again, you may need to experiment, or better yet post up and start a thread about it... the group here loves these threads.
My setup? Side of the fender, passenger side. It's out of the way pretty much all the time unless I'm changing my air filter. It's the second best ground plane (best is roof). It's fixed to the fender so it doesn't smack the roof or roof rack when I open the hood (unlike a lip mount), a 1/4-wave antenna lets me keep in installed all the time and still get in the garage, and I keep a full-length antenna under the back seat for trips, and I rarely notice it while driving. It's my 4th location and the one I'm sticking with.