By itself, the wood siding won't give you large insulation gains.
This chart, for example, give wood lap siding an r-value of .8. They don't specify a thickness, but that'll be in the ballpark.
http://www.coloradoenergy.org/procorner/stuff/r-values.htm
Stripping the siding off
would give you the opportunity to build Larsen trusses, though, like here for example:
http://www.builditsolar.com/Projects/SolarHomes/LarsenTruss/History.htm
That's just a wall system that gives you lots and lots of
room for the insulation material of your choice. Then you put on the outside of it whatever type of siding you prefer.
Good luck!
Mike