the switch by the distributor is the actual oil pressure sensor, the one by the oil filter is for the light on the dash so if the pressure drops too much it will turn on the light. The one by the distributor actually disables the ignition if pressure is lost.
as for the wrench light flashing on the dash? It may just be telling you there is a problem and to do a diagnostic by jumping out the diagnostic plug on terminals A and D. (it is a square or oblong 4 terminal black plug, located either by the ecm or on the wire harness somewhere back in the engine compartment). On smaller trucks it is under the floor plate on the RH side.

Using a Diagnostic Jumper to Diagnose the ECI System
If you do not have access to a laptop computer, it is still possible to access the diagnostic trouble codes stored in the memory of the Spectrum system ECM using a diagnostic jumper and the malfunction indicator lamp. With the key OFF, connect the diagnostic jumper to the DLC located near the ECM. The jumper will connect diagnostic pins A and D. Turn the ignition ON but do not start the vehicle. The malfunction indicator lamp (MIL) will begin to ?ash.
The MIL displays three digit codes by flashing the first digit, pausing, then flashing the second digit, pausing, and then flashing the third digit. There will be a long pause between codes. For example, a code 143 would be one flash followed by four flashes followed by three flashes.
The MIL will first display a 166 three times. Code 166 indicates that the ECM based diagnostic routines are functioning. Then, any Diagnostic Trouble Codes stored in memory will display three times each. The MIL will then start over with the code 166. If the vehicle is started while the diagnostic jumper is in place, the MIL will flash rapidly.
Diagnostic Trouble Codes may be cleared from the system ECM memory by moving the ignition key to the OFF position and removing the (F2) system battery fuse for at least 15 seconds.
NOTE: This will erase all of the memory in the computer including the adaptive learn.
Follow this and you will get the codes.
There are too many codes to list here so just get them and i can tell you what they mean.