gil: dont do it! the risks are far to great to mess up a gun as valuable as a westley richards.
however, you might consider the following approach. sent a gun of lesser value to the case hardening mechanic as a trial project. if he destroys that one, then you have learned a valuable lesson, without damage to your fine gun.
also, consider the affect of receiver rehardening on the resale value of your richards. regardless of how successful the mechanic is in recoloring your receiver, the gun will always carry the stigma of having a non factory rehardened receiver of unknown quality.