[StormEye]

"The President can nominate a replacement but both
houses of Congress must approve."

Only the Senate approves a nomination for VP.
The House of Representatives has no say in it.

[olesigh]

Amendment XXV

Section 1.

In case of the removal of the President from office or of his death or resignation, the Vice President shall become President.

Section 2.

Whenever there is a vacancy in the office of the Vice President, the President shall nominate a Vice President who shall take office upon confirmation by a majority vote of both Houses of Congress.