hello everybody not sure if it been posted but my question is....i bought S4 DCC Erie #528 is it possible to upgrade this Loco to have soundtraxx or do i have to buy one that is equipped with the soundtraxx such as the S4 DCC #529 already installed,and if i can upgrade at a later time for the #528 what would be the stock number for the soundtraxx part...sorry for the question but it's been 40 years and now I'm just getting back into HO scale seen ...so much has change in the last 40 years.....