Technically, you need a molex remover and some new molex pins for the size molex connector you're using, both easily available from bob roberts.
A much harder solution is with a jewelers screwdriver, you can bend the tiny pins holder the connector in, and pull the connector out, bend the even tinier crimp holding the wire on, remove the old wire, and crimp the new wire back in. Then bend the pins back out, and insert the connector back into the molex.
Not that hard all in all, it's just VERY TINY pieces of metal.