Hi
is there a way to have a female sim have default male hair and/or clothes, for example?

Sure, but you have to remesh the hair and clothes to fit the opposite gender (except for toddlers/children - those are easier and you can just change some values in the recolour files). If you know the basics of meshing hair/clothes, it should be pretty easy. If you don't know the basics of meshing hair/clothes, you'll need to do the basic tutorials first before trying a gender conversion.

Where do I find the basic tutorials needed?

Over in the Body Shop Meshing forum - you'll want to do the Unimesh clothing tutorials first before trying anything related to hair.