You cannot change just the DMD chip, you will need to replace the DMD board.
The board is not going to be rocket science to change but its not a walk in the park either.
It basically consists of taking the set apart, finding the dmd board which is going to be almost right in front of you, unplugging some delicate wires, taking out the screws holding the dmd in place, taking it out and putting the new one back in. One of the hardest parts is after you replace it you will need to align the new board. This takes two people to make it easy, one is in the back moving the board around until the one in the front says its good. This is also the most dangerous part because your hands are in the set while it is on, one wrong move and you will get hurt or destroy your new board or worse your set.
The part number you need depends on the serial number, if you give me the serial number off the back I can do some research and get back to you in a few hours with a part number. Both boards that it could be are around $200.
Please let me know if you have more questions or would like more information.
If you would like any additional information or have more questions please don't hesitate to ask!