It would have been much better for Rehnquist to retire first or at the same time, as a conservative replacement for Rehnquist doesn't change anything. O'Connor is the fifth vote for legal abortion, which means the hearings will be all about one issue, and one issue alone. Abortion. The Democrats will not compromise or yield on that issue which means filibusters and character assassination. It means no replacement will be forthcoming anytime soon.
If you thought the Bork treatment is bad... you ain't seen nothing yet. This will be the ugliest fight to take place in the Senate for a long long time.