DCC installing decoders

[kingraptor]

hey, i want to switch from DC block control to DCC for my West Virginian and allegany rr and have no idea how to install decoders. does anyone know any of the following questions?1. what decoder do i need for a bachmann gp-38-2? 2. what decoder do i need for a atheran GP-40-2?, for an atlas u-33c? for a bachmann gp-40? and how do i install them, please help me!!!!!!!!!!!!!!!!!!!!!!!!!!