Does this come with all necessary parts? If not, what other parts must be purchased to use it?

It comes with everything you need to have instant hot water at one sink (mine is in the master bedroom). To hookup the pump to the hot water heater I used a 4 inch 3/4 iron pipe. To connect the pump to the hot water out line to the house, I used a 3/4 inch flexible pipe. If you want another sink to have instant hot water such as the kitchen you only need the manifold kit (usually @ $25).