The new TVs have a digital tuner or QAM tuner built in them and that is required in order to receive a signal after Feb. 2009, if your are using an aerial antenna. You will still need an antenna outside though to receive a signal. If you already have one it will still work. Like I said before you just need to make sure the new TV has a digital tuner in it. Most will and it is required by the government to clearly labeled any that are not.
The new TV's do not have built in antennas. They have built in "digital tuners" for an antennas, so that you would receive digital signals.
How do you receive reception on the TV your replacing? If you have an external antenna it would connect exactly the same. The only difference is that the the new TVs will work once the Febuary 2009 convertions take place.