We currently offer a massive range of downloads for FSX, as well as older flight simulator add-ons for the ever-popular FS2004, FS2002, CFS3 and now becoming ever popular with dediced virtual aviators is Laminar Research's X-Plane series.
I am trying to learn the prop planes and some of them are vastly different I am discovering. For starters, I can't for the life of me find the altitude, speed, and GPS headings for both the airplanes I listed. I bring up the main panel (shift+1) and look all over. For one of the planes (forgot which) I found the GPS/NAV switch, and the master autopilot, but I couldn't for the life of me figure out where/how to set the altitude on these things!
RE: set up the Autopilot on the Grumman Goose and the Douglas DC planes
I usually use shortcuts whenever I can, much better than using the mouse IMHO and they work really well when flying the big jets:
Z: toggle autopilot
Ctrl + Z: toggle altitude hold
Ctrl + H: toggle heading hold
Ctrl + N: toggle nav1 hold
Ctrl + A: toggle approach hold
Ctrl + R: toggle speed hold
Shift + R: arm auto throttle
You can adjust the bugs by pressing the combinations below and then using + and - to adjust the values:
Ctrl + Shift + Z: select altitude bug
Ctrl + Shift + H: select heading bug
Ctrl + Shift + R: select airspeed bug
You'd have to set a shortcut to toggle GPS/NAV manually, I usually put it on Caps Lock. There are more shortcuts for the autopilot, check the FSX controls options!