You will want to go with the Mustang MAF system from between 89 and 93 which means you will need a 5.0 Distributor, Mustang wiring harness, Mustang ECM, ECT sensor, MAF unit (sensor and housing), possibly an ACT sensor which will need to be mounted into the intake, BP sensor, fuel pump, inertia switch, and O2 sensors. I think that covers everything. Basically from what you listed you need the intake along with everything connected to it. I.E. Lower and Upper, Throttle body, injectors, fuel rail, fuel pressure regulator, idle air solenoid, and throttle position sensor. I wouldn't even attempt to use the Explorer wiring harness. It is a lot harder to get working and would require a lot of other changes to the motor.
As far as the deal for it I think it is a fair price. I've seen the intakes go for twice that on Ebay.