First of all, I'm not a taker on the project. I have another similar project I'm working on for a client, however, so I have a pretty good idea of how this sort of thing is best accomplished.
Any images you take or acquire will be of assembled gauges. Then these gauges will likely have an indicator needle present. Finally, they will have glass over the face of the instrument.
The most realistic gauges in Outerra would be based on 3D elements. Therefore, you would have a gauge indicator face, an animated indicator needle or needles, finally covered by a semi-clear surface. All of which need their own textures -- or photographs.
If you had an excellent series of C172 photographs taken under very controlled conditions, you would still need to Photoshop them to remove artifacts induced by the clear face and you'd have to carefully remove the needle to create your background. The needle gets reused, and of course you'd have to do some sort of baked reflection for the transparent face.
So you never do get away from Photoshop, and it's far from just a matter of cropping images. The key thing is the controlled environment for the original images, and this is something you, as the creator, really should do yourself with a decent camera. Since this is your baby, you'll want and need complete control. It's a great idea to give a try, but a team effort would probably be a lot more cumbersome than just going to the local FBO and describing what you want to do. Don't be rebuffed by the first rejection, you'll eventually find someone willing to let you spend an hour or so in his aircraft...under supervision! Good luck!