I got a quote for an STEC 50 auto pilot into a 172N - $15 to $20,000.
However I found that fitting a Dynon D10 efis and autopilot was only $13,000. Included in this cost was about $1,100 for an engineering order to fit non-STC modification to a certified aircraft.
Not only was it cheaper but I get a second A/H, altimeter, airspeed, DG, etc etc - vastly safer for IFR/night stuff!
Not sure if you can do this in Brazil but I think it would be well worth looking at.