i have a undec wood cab and want the steel cab, can they be changed easily and does anyone have one to swap or sell?

Thanks,
Jim

Recently bought this loco and found a small plastic bag with what appears to be a circuit board. I'm new to DCC and have no idea what it's used for? Come on Bachman include some sort of instructions with your product so guys like me aren't confused!

Recently bought a S4 that was marked as DCC Ready. What do I need to make it active and can I add sound?
New to this part of model railroading so any help to get me up to speed will be greatly appreciated!

Thanks,
Jim of Medford Trains