You need to go to a site such as Tony's Train Exchange and read his DCC Primer and learn what is available.
http://www.tonystrains.com/tonystips/dccprimer/index.htm
DCC decoders generally allow their locomotives to be run with a DC powerpack unless they have been specifically programmed not to (not the normal factory default). When running DCC equipped locomotives with DC your throttle won't have the range of speed control that it has with a DC locomotive because the decoders usually require a level of 6 volts before they can recognize that they are in DC mode and begin operation.
The most popular way to get into DCC operatons is with the purchase of either an NCE PowerCab or a Digitrax Zephyr. Of the two, the PowerCab us usually regarded as the easiest to learn.
Best!