Welcome to the forums.
I'm not an N scale modeler but can give you some hints. Was the particular model ever offered in DCC/sound? Does it have a motherboard with an NMRA plug? Have you checked the TCS website for installation pictures?
Pete
Are there any updates on how to install a sound decoder in an n scale Bachman spectrum 2-6-6-2. Also what brand ? I presume in the tender, but pictures would help too. Thanks.