You don't need to drain the filter bowl. Only a few drips will come out.
Insert adapter.
Use the 90* m/f. You need it to give you some room for the transducer wires pushing on the coolant line.
Screw in the transducer.
I should send you back to eBay; it's all there.
Input: 0-100 psi.
Output: 0.5V – 4.5V linear voltage output.
Wiring: Red: +5V. Black (yellow): ground. Blue (green): signal output
Wiring: 5v from EGR is BR/w to Red on pigtail. BL/gr to DashBoss. BK/y back to DashBoss and ground. You must ground this wire to the truck frame and the DB; the cab near the DB is preferred. This wire from the DB will test as a ground, but it floats in the circuit and will not work unless tied as a chassis ground.
Set your voltage input to the values above for correct PSI reading. BTW, you could use one of the unused wires in the engine bay, driver's side, upper rear for the through the firewall connection, if you wanted. They come out near the parking brake.