Chrysler Repair: PT Cruiser Mopar Oil Pressure Gauge, oil pressure gauge, chrysler pt cruiser

Question
Hello. I have a 2005 Chrysler PT Cruiser GT, 2.4L high output turbo. I recently bought a Mopar oil pressure gauge and boost gauge from Mopar parts dealer online. When I took them to the Chrysler dealer for instal the service writer assured me it was no problem.
When I returned, I was told that since my stock oil pressure sending unit had to be removed for them to instal the one that came with the gauge... The red oil can light is now on and there's no way to get it off. I was then offered to pay another $300 to have the gauge and it's sending unit removed and go back to original configuration, as this was the only way I could have the oil warning light de-luminate.
It's been a month since then, and most of the time the oil light is off, it illuminates about once a week and goes away when the car is turned off and starts again.
I went to the dealer expecting to find experts, but clearly am dealing with amateurs. Have you seen this before? And moreso what should I do to get this rectified at the dealer?

Answer
There was nothing shown in my wiring diagrams for a signal for the pressure gauge, just wiring for the light. It would seem to me that the installation must have involved wiring the gauge to the new sending unit. The new sending unit probably simply has a pin for the warning light wire to be attached to, and then another pin(s) for the pressure gauge signal/power supply. If that is the case, then it would be hard to see how it could have been mis-installed unless there is a flaky connection of the warning light wire to the sender or the sender is no good.
So take a look at the wires on the sender to see if one of them may be shorted to the block or to some other metal item. That warning light wire is gray in color and is routed to the powertrain controller.
Do you have the instructions for the installation? I don't see anything about this gauge as an option in the '05 manual. If so, does it say anything about a modification needed with respect to the warning light other than simply plug and play?
The next time you have the malfunction, with the engine still running, remove the gray wire from the sender which should turn off the light. If the light stays on then there is problem with that gray wire being grounded falsely. If the light goes off, then there is something wrong with the sender and you should take it up with the vender of the new unit.
Let me know what you learn.
Roland