to address stairs from basement to main level of house. right now they are standard 2x's..riser and header. i have been looking at retro stair treads. is this the way to go or to try and remove existing riser and tread to put in nice finished oak treads?
By header I'm going to have to guess you really mean a stringer, that what the risers and treads are attached to.
What's "retro" treads? If you mean factory made stairs, there fine in new construction but can be a pain to get inside and in place in a finished house.
No one here can see what your seeing without a picture.
If your currant stairs run, rise, headroom, width and railings meet current codes and the stringers were constructed and installed correctly there's no reason to not work with what you have.