The new 45 tonner only (AFIAK) comes with DCC already onboard.
Yours, the 44 tonner, says it's DCC ready, but I've never had anything but grief trying to use the circuit board they have in it to wire in a decoder. It doesn't have a socket, it's got 4 holes in the circuit board where you're supposed to solder in the leads from the decoder. I've tried this on several locos, and the decoder always acts twitchy.
Your best bet is to rip out the circuit board and wire in a Digitrax DZ125.