A primer on DIY solar surveying:

http://www.builditsolar.com/SiteSurvey/site_survey.htm

Dig around on Gary's BuildItSolar site there- there's TONS of information relevant to your project in those articles & links.  Poke around on heating sites as well...

Hard chines,
That is one nice looking barn, I think I would find another place for the goats and old tractor,
Good luck on the solar panel hunt,
Dan
Have a look at this site, this is the Thermal wall collectors I mentioned,
http://www.thermo-dynamics.com/

Dan that looks neat, it would be a bit of a trip but I wonder if they would mis lets say ten panels, LOL.

Thx on the barn its my toy barn," NO ANIMALS ALLOWD" .