Mario,
the Bachmann mogul will need the suppressor caps removed from the motor terminals if converting to DCC. Basically, you need to separate the track pickupds from the motor supply leads. In so far as sound then how big a wallet do you have? You can pick up a dodgy MRC 5 amp decoder for around $70 with motor and sound capability and up to several hundred dollars for a dual decoder (motor and sound control). If just after motor control, the 4 amp NCE decoder is bulletproof at around $70, or many seem to go for a Digitrax decoder.
If after separate sound to the motor decoder then Phoenix is hard to beat. The Phoenix PB8 is designed specifically for DCC and the PB11 may be used for both DCC and analogue operation if you wish to run your locomotive on an analogue track at some time in the future. While a NMRA DCC standard requirement to provide facility for running a non-decoder locomotive on DCC track power, many American manufacturers have deleted that facility from their systems. Keep this in mind if you at some time may feel the need to run an analogue locomotive on your DCC track (not a desirable proposition as motor damage is possible).
My advice is to look up the Mylargescale forum and go to the DCC section of that forum. There are around twenty pages of postings that will give you an idea of your needs. I do not think any single person can guide you as each has his own biassed preference as to an operating system and preferred brandname decoders. Basically, you need to do a little web browsing.