nice work,
the retopo tools can be a pain but there is a good tutorial by someone on this forum, check the tutorials board, im sorry but i cant remember who did it but will see if i can find and post a link
the mental ray sss is also a difficult one, not only does the result depend on the shader settings but also the textures you paint and use also,
not sure what software your rendering with but gnomonology has a great 3 part breakdown on that particular shader and i think its about 12 bucks. other than that there will be alot of info in the help of your particular 3d software.
dave
update: here is the link to the retopo tut and many others
http://www.zbrushcentral.com/zbc/showthread.php?t=53087
and the sss tut
http://gnomonology.com/group/15