I would like to convert the rapidos on my Spectrum 2-8-0 starter set with knuckel couplers.  From what I've read in this forum I understand that Bachmann has converted their new sets with new couplers.  My question is this:  What coupler can I purchase that is easy to install without making any modifications on the Bachmann tender and rolling stock?
Thanks, Bob 

I have a 2-8-0 and run on DC.  Can anyone suggest which sound decoder I could purchase to install?  Also, is it easier to install it in the tender?  I am new to the hobby and need something relatively easy to install.  Any help will be appreciated.
Thanks, Bob