I was able to take the pins out easily from the old drivers, so ended up just ordering the valve gear assembly.  However doesn't solve that the assembly only comes in black.  Will have to live with my Franken Prairie for now =)

I accidentally gripped hard the flanged driver wheel with the eccentric steam rod and the tiny eccentric rod (kind of shaped like a tiny "Z") snapped in half.  So crushed!!  Tried gluing it but it didn't hold for a day.

I removed the entire assembly and looks like the spare parts store only sells the assembly in black or red. 

Would it be possible to just buy the valve gear assembly:
https://estore.bachmanntrains.com/index.php?main_page=product_info&cPath=70_78&products_id=7696&zenid=q8cvaufb3k3ugihdo4nioqc4r4

However I don't see any screws to enable the replacement to the wheels or to the green plastic piece, just pins and riveted heads.  Sort of confused how I can fix.