B4 and after ;)
  http://svoshsphotos.fotopic.net/p13421934.html) 
 basically you use [ g] max to edit the vert locations of any part you want in the Editable mesh level of the stack Just as Taina's read me says. NO operations , no cutting no attaching no welding no collapsing , the better you are, the better it will be, you also can edit uv cord and replace them as well a very handy tool  
 the lips are only fuller in the profile shot you can see the difference anyways you get the idea ;) 
 EDIT : here is the link to the tool for those that want to see what they can do   
http://www.pcgamemods.com/mod/11335.html)  
 Follow the read me to a T, don’t rename any model sections in max and unlike chuck’s replacer this is a 6 part deal and very unforgiving one mistake and the app generates an error or crashes. 
 A good understanding of 3d modeling is good to have but don’t be intimidated by XYZ ;) 
 Good luck  
 svцsh