If you haven’t done a Callaway bore through iron before, you might want to send it to us or have someone experienced with that kind of repair do it. I am assuming it’s graphite, which actually makes it easier than steel on the bore through irons. If the shaft your removing is intact, then a graphite shaft puller would be needed. A heat gun would be used as the heat source. With the proper shaft puller and heat gun, the procedure would be pretty much the same as removing a graphite from any type of club. See the link below.
Installing a new shaft in the bore thru requires a few more tools to finish off the bore thru. You will need a bore through pin (BTSPGV) to install when you epoxy the shaft in place. The shaft goes through the bore thru hosel and the pin is installed using epoxy at the same time you epoxy the head in place. Once it is cured, you will need to finish off the sole. Ideally you would have something like our Multi-tool sander (MT0008) with the proper belts to finish off the sole ( sanding NT001 / finishing MT0004). You may not want to invest in all of that for one club, so you can finish by hand by sanding or cutting the protruding shaft off flush with the sole. To do it as cleanly and professionally as possible you would need some kind of way to sand the bore thru pin and shaft tip down flush with the sole.
As far as what type of shaft, I would need to know the specific shaft that your replacing to be able to recommend a replacement.