Welcome, rejdavid.
I think makehuman is what you're looking for:
http://www.makehuman.org/blog/index.php
When you're finished configurating your model, save it as OBJ (click the OBJ disk icon, hit Enter to save in the default path) and then import it into SketchUp using the OBJ importer:
http://www.scriptspot.com/sketchup/script/obj-importer