We haven't converted "Ding" yet, but I will be doing it myself. Looking at the Roadmaster EZ4 base plate and the Roadmaster Falcon 2 tow bar from eTrailer.com. Comes in right around a $1000. Installation on the Soul is actually pretty simple. After talking to my mechanic, think we are going to skip the breaking system for now. The Soul is such a light vehicle, he said we wouldn't even know it was behind us!
We also just added the OEM Cruise Control ($70) and a draw-tite trailer hitch ($100) Very easy self-installation. Loving the simplicity of Soul. Perfect toad!