Since you have screwed-on OSB wall covering, you've got couple options:
a) Take all OSB down and put up roll bats of insulation with paper vapor barrier on warm side (ie inside)
b) Take all OSB down and staple up plastic barrier and blow in cellulose insulation like couple GJer's have done through hole in plastic at top of each wall cavity
c) Take all OSB down and have foam insulation sprayed (closed-cell or open-cell) - - - these are expensive options, especially closed-cell
Of course above options are AFTER you've done all your rough electrical and lighting upgrades. Also plan 240v runs for compressor, welder, etc while you are planning out your electrical upgrades. I'd go with either a) or b) and do the "Canada style" vapor barrier taping of each electrical outlet so you don't get any air infiltration at those. Good luck.
P.S. Who are the hot brunnettes in your Photobucket album, and what is story on broken suspension on the Dodge pickup ????
