Huck is correct on the installation, and that the Cobra 29 is a good radio. There are a couple of things I would add, though.
First, when you run wires under carpet, make sure they are not in a place that would allow them to crimp, chafe, or break.
When you choose an antenna, get one that can be "tuned". A CB shop, or a friend that knows CB's or Ham radios can help you. Tuning is extremely important, as it not only affects the performance of your radio, but, if not properly tuned, an antenna can cause damage to the radio.
Other radios to consider would be the Cobra 25, or the Uniden PC68 or PC78. All come with choices of options, like weather channels, etc, but none should be more than $125 or so. A Cobra 25 or Uniden PC68 with no options can be had for around $70.
If you have unlimited funds, you can buy a 10 meter (ham) radio and have it converted to CB. I have about $275 invested in one, and $450 in another. Expensive, but extremely durable.