I have a 401(k) plan that has as a distribution option installment payments figured over the life expectancy of the participant.

Say a person selects this method. But three years later, she wants/needs the money. Can she cease those payments and take a lump-sum distribution for the remaining amount?

In most plans, this will already be determined by plan provisions.

If this former EE quit before reaching age 55, began taking the installments over his life expectancy, no more than 5 years has passed or is under age 59 1/2, then by taking the lump sum he might face the 10% early distribution penalty on amounts already taken.

As David said, yes, assuming the plan document allows.