Dave,
If you already have a Dynon EFIS then it might make sense to install their autopilot. That said, I prefer to have a seperate and independent source of heading and turn rate information. So, I chose to install the Trutrak Digiflight II autopilot. The Trio autopilots are quite popular as well.
The roll-axis autopilots are simple to install. The ones with a pitch servo require a little more imagineering but it can be done.
Rick Pellicciotti
EZrg N818KD, Race 51