You can save the face of your 'face' character to the Faces library, then apply it to your 'body' character. As long as you have the required morphs injected beforehand, that will work. Morph Manager doesn't know about pose injection. The hierarchy editor can show more parameters - you just need to check the 'show all parameters' box (not near a copy of Poser right now, so the wording may differ). You can do things such as deleting and renaming morphs etc. within Poser. However it isn't possible to swap heads between figures in this way. An easy method is to bring both figures in, hide the body of one and the head of the other; this will inevitably leave you with some nasties in the neck area to be postworked away, but to get closer you'll need a 3D modelling application to make a new mesh.