To change the hair, just navigate to the null called Mesh> head stuff>Hair
Here you can hide the hair you don’t need and show the hair you do need. Use the traffic lights.
You can alt+click on them to hide both in viewport and render at once.
Any objects you place into the “head stuff” null, will follow the head.
Similar approach is with the clothes, just hide and display the clothes you need.
Hold Stuff in hands?
If you want something to be held in the hand, find the “hand stuff” null and place the object in there.
Great for swords, suitcases, baseball bats etc.