Hello John, there are other people here who know a lot more than me about painting skins, but you could try Simmer's Paintshop for tutorials. You'll need a decent paint program, but you needn't go the length of Photoshop; perhaps the best skinner for CFS3 uses Paintshop Pro and the nVidia plug-in for importing/exporting .dds files for CFS3 skins works with both Photoshop and Paintshop Pro.
To build models for CFS3 you will, as mentioned, need gMax. For tutorials on using this, see the Aircraft Design and Animation forum here at SOH, but you'll need to work through the tutorials supplied with gMax first. Be warned that it's not easy, it'll take serious amounts of time and you may lose your sanity, but the satisfaction of seeing your own model take flight in the sim is considerable!
Simmer's Paintshop
http://www.simmerspaintshop.com
Gryphon Painting tutorials
http://www.simviation.com/gryphon/Tutorials.htm
nvidia plug-in for .dds files (Photoshop or Paintshop Pro)
http://developer.nvidia.com/object/photoshop_dds_plugins.html
Aircraft Design and Animation forum
http://www.sim-outhouse.com/sohforums/forumdisplay.php?f=22
and you want the sticky
New links for old for Milton's excellent gMax tutorials
Other gMax tutorials include Viso's Bitmap to Boom'n'Zoom and Hugh Shoults' Stupid Idiot's Guide to gMax.
Bitmap to Boom'n'Zoom
http://www3.telus.net/murrdaka/tutorial/B2BNZ.htm
Stupid Idiot's Guide to gMax
http://www.simviation.com/gryphon/tutorials/gMax_00.htm
Any more questions, just yell! :welcome: