Probably. It really depends on what the 5 positions are. If you don't need a four conductor and purchase it it won't hurt anything. It will give you more options on wiring. When I bought mine five years ago there was no upcharge for the four wire version.
Yes you will need a 4 lead pickup. That 5 way will have coil splits in position 2 and 3 for sure....depending on wiring even #4 could involve splits on the neck pickup.