CAN I FIX MY BMW 320D 2005 NEW SHAPE MY SELF?

320d 2005 new shape yellow warning light on dash TRIANGLE WITH CIRCLE AROUND IT D.T.C switch on dash dose not work ABS OK DO I NEED A NEW UNIT I HAVE BEEN TOLD THAT I MUST FIT NEW BECAUSE A SECOUNDHAND WILL NOT WORK BECAUSE YOU CAN NOT PUT IN NEW CODE IN IS THIS CORRECT REGARDS HAYDN