How much work to replace 1995 Plymouth voyager water pump?

Neither one. The 3.0 requires the removal of the timing belt, and unless they changed design, the removal of the intake manifold. Also, under the intake there is a "water tube" which is prone to rusting out and leaking. Done 4 of them (pre 2001) my best time, 8 hours not in a shop. But I have been a licensed mech. for over 30 years.and have all the tools and air.