Bach Man

I have a Bachmann 4-4-0 that I am interested in adding a sound system.  I understand it is prewired for a sound system.  What system would you recommend for this loco?  And what all is involved in setting up the system.  Thank you for any information you can give to me.

I am new to G scale and would like to build a shelf layout in my family room.  This layout would have to be up high on the wall.  The size of the room is 14' by 45'.  I have read several of the topics on the message board and still have questions.
          What is the minimum distance from the ceiling needed?
          What is the minimum width of the shelf needed for a double line?
          What is the minimum radius I can use?  I have a 4-4-0 American now
                   and would like to get a 4-6-0 Pacific, 2-6-0 Mogul or 2-8-2         
                   Mikado if the minimum radius needed is not to large.
Thanks for your help.