Decoder for my new Athern SW1500

My wife bought me anew SW1500 from Athern and I want to install a decoder with sound.

The Problem is how to remove the shell. Ihave been looking at it for a week now and dont know where to start. This is my first try and I dont want to mess it up can any one point a clueless man with no idea where to start

Thanks , clueless

It is very tight in there. I would suggest a LokSound Micro. The MRC and Tsunami decoders that Athearn has used and will be using are of a special form factor for this loco.

David B