fan won't come on?

The first thing i would fix is your large coolant leak then trouble shoot your cooling fan.If you go to auto zone you can rent a cooling system pressure tester and the adapter's to screw onto your coolant bottle.Then you can pump up your cooling system to find the leak.It's a free rental you just have to leave a deposite.Let me know when you have that leak found and we will go from there.

I think what you are referring to is the clutch assembly? A lot of times salvage yards take motors apart and sell them without the gear that actually engages the flex-plate to start the vehicle. Basically they expect you to swap that over from the old unit.

Let us know if this is the case or if you need more assistance and we can dig deeper. Thanks