ok, i assume you use o2 to retexture the model, right?
and i assume you already have some textures to swap.
- to texture the arms, select the selection named "-!!!!", go to face properties and simply change the path to your texture.
- for the body: select "body injury" and do the same.
- for the legs select "l leg injury", hold down "strg" and select "p leg injury" -this should select both legs. click on the face properties button (that little triangle with the 'i') and again change the texture path...
that's the easiest way to start.
hope that helps - if you still have question, just ask right away