Hey Guys, needs some help, advice here,.....

2005 Pont Bonneville SE, 3.8 L

Headlights come on and off at will.
Dash lights and gauges come on/off at will
Power Locks have stopped working
Security Warning light comes on and off
I installed a new battery a few weeks ago. All posts are clean.
The auto parts store tested the alternator and said that it was working properly.
I had a shade tree mechanic clean the grounds. He said he got to all of them.
Still continues to act freaky.

I hate to give up on this car because the engine runs good.

I then took it to a Auto Electric Shop to help me with the diagnosis of what is the cause.
The Technician says that he is getting a Code of bad module.
The only problem he says is that it doesn't tell him which module is bad.
He says there are seven, and he would have to go thru each one to disqualify each one he said.
He says that they all have to work and communicate with one another.
Dash, ABS, Engine, Power switches, etc etc.
He says the lengthy diagnosis would end up being more than what the car is worth.
I'm wondering if I would be able to check these modules myself?
If so which one should I start with?
Any other suggestions ?
Is there a more advanced code tester which would show which one?

Or, is this info I'm receiving correct?
Thanks Much!

If I could just get the headlights to stay on, and for the Security chime to stop, I would be satisfied.

When I hear "at will" in a description like this, I take it to mean "at the will of the driver" . . .

. . . however, this sentence makes me think that you are saying that the headlights and dash lights come on and off at the will of the demons infesting your car at the moment.

Which one is correct?

I assume your auto electric shop charged you for their diagnosis. Can you post a picture of the bill/invoice? I'd love to know what the code was. There is no code that will tell you a module is bad but not which module.