actually, i think the second would be pretty easy.  you don't need GI that much.  notice how her chin is not more red despite its closeness to her skin?  and her ear and arm are a bit more red, which isn't from anywhere in the environment.  HDRI and IBL would suffice, or even just plain LDRI and IBL.  i'd say a look at the bagginsbill threads on VSS, his environment sphere, and his IBL tool.  oh, and if you use spotlights (which you wouldn't for an outdoor shot), make sure you find his inverse square falloff script.  that will help immensely with his lights.  you can find it by searching in the forums, and it's been longer than 45 days.

and if you don't have Poser, grab Pendragon's free ahEnvironment Light 1.0 set for Daz|Studio. and his free hair shader.

the first doesnt' look high quality at all to me.  it looks about Preview quality almost.  it's so stylized i'd suggest playing with materials and lights until you just get it.  it looks like a edge blend nodes would help with the background, and possibly with all of the materials.  they look rather "glowy."

thing is, no one can tell you how to duplicate someone else's artwork in one step. especially when someone else is actually a whole team of people.  my suggestion is to just try different things.  in the first case, i'd try a medium ambient light, some colored spotlights, and just some real experimentation when it came to the materials.  in the second, i'd use mainly ambient light in the form of IBL and then an infinite light.  then i'd learn everything i could about realistic  materials.  good luck!