Is that straw color natural or dyed? If it's dyed, way too many color processes and you will wind up with orange hair. Use a color remover and plenty of a deep conditioner. If that is natural, I would darken it gradually.
Darken it gradually. That's a drastic change, and if you go to a dark auburn, you will wind up with medium or light auburn.
Try on a wig first. Make sure you really do like it. I have found our skin seems to match our natural shade better.