I want to attach stock Yoda's head to the stock jedi's body. Is there a specific tutorial for that?

I don't know, but What i do is: is I press the y key and highlight all the the polys and go to create poly msh and select extract keep the export it and imported it with the Jedi then delete the head of the Jedi and put Yoda's then envelope the Yoda head to the bone_head

Without sounding like an idiot you're also using XSi right?

yes