There is the entire sprinter manual in the techdocs section here. Has a great foldout wiring diagram for the entire car.
Check club4ag for the 4age wiring diagram. There are probably a few different ones so make sure you know what your engine is. Build date can be found printed on the plug leads, or any other wire in the loom for that matter.
Wiring one of these thing isn't too hard because your 4ac had only 2 wires going to the engine, so there isn't much splicing into existing electrics in the car that is needed.