Question:

Is Matthew 18:8,9 only to be taken as an illustration?  Can it be taken literally?

Matthew 18:8, 9: “And if thy hand or thy foot offend thee, cut it off and cast it from thee; it is good for thee to enter into life lame or maimed, rather than having two hands or two feet to be cast into eternal fire. And if thine eye offend thee, pluck it out and cast it from thee; it is good for thee to enter into life one-eyed, rather than having two eyes to be cast into the hell of fire.”

As mentioned in the former question about verse 9, if we are living in the power of the Holy Spirit, we can get the victory over sinful tendencies, and literal mutilation of our body will not provide any additional help.  Cutting off hand or foot or plucking out our eye would hurt, and breaking sinful habits may hurt, at least for a while, until these are replaced by Christ-centered habits.