If budget is a consideration you could buy two Dynon servos and connect them to the D-180.
The bigger question is what is going to drive the AP? You will need a GPS enabled moving map for flight plans, etc. Ideally one that will display weather and traffic. Budget minded options to consider would be the Garmin Area 760 or Ifly 740. There are also older GPS models available on the used market that could also easily work.
All it takes is time, money and effort!
First Flight 11/13/2011
TMX0360, Dual Pmags, CS