It doesn't sound to me like you have a problem. Think twice before you throw money at it.

I'm not sure what you mean. There are 2 possibilities:
1. The Sender Unit is not working and the gauge is displaying false information.
2. The Sender Unit is working and there'* a problem with the oil pressure because of the engine wear or oil pump.

So should I ignore it and continue driving the way it is. Again, the engine'* got 130K miles. I'm not sure if engine wear is typical at this mileage.

The sender is a really easy replacement. On the passenger end of the engine, on the side near the firewall, there is an aluminum casting that bolts onto the block. This casting is where your oil filter is attached and where the sending unit attaches. Unplug the electrical connector, unscrew the old one, screw in the new, attach the connector and you're done. But that same casting is where the oil pressure relief valve is located and that'* what your mechanic should also be checking before you think about the oil pump. I would think it is much more likely that the relief valve is sticking than any fault with the oil pump itself.

The oil pump is an integral part of the the timing cover on the front of the engine. A lot of stuff has to be removed to get the cover off. This is a much bigger job and will cost you a bunch. But I would be very hesitant to have this done. These oil pumps are directly driven from the crankshaft and very rarely fail.

[edit: I agree with the others responding here that there does not seem to be anything wrong with your car. I don't know where you heard of a "safety level" on the oil pressure gauge. On an older engine, as the bearings wear and develop clearance, It is normal for the oil pressure to drop with engine speed and increased oil temperature. Especially if your oil pressure returns to a more "normal" 40-60 psi when your engine speed increases to 1500- 2000 rpm, you have nothing to worry about. The best thing you can do to prolong the life of the engine is to change the oil and filterfrequently and use a quality oil.]

What I'm suggesting is that the pressures you posted don't seem too low. They seem perfectly normal for a 10 year old car with 130,000 miles.

Is your temperature gauge showing that your engine is hotter than normal when you observe the low oil pressure? As your engine temperature increases, the oil will thin, and the pressure will drop, so make sure this isn't just a thermostat going bad, or a cooling system problem.

Did this drop in oil pressure occur suddenly or has it been developing over a long period of time? If this pressure drop just suddenly appeared one day, and your engine temperature is what it has always been, then that suggests a relief valve stuck open. If the pressure has been getting gradually lower at idle over a long period of time, and the temperature is what it has always been, that would suggest normal engine wear.

Other problems are possible, but not as likely.

The oil pressure has been dropping steadily over the past 6 months. The engine temperature reads about 225-230F. Is this normal? I'll have the mechanic replace the thermostat if necessary. Should I change it to a lower temperature (160F)?

crod101 do you have a oil cooler on the drivers side of the radiator? I've noticed that they usually have lower pressure. As long as it is not bouncing I wouldn't worry about it my Port has 260,000 miles on it and it gets down to about 20-25 at a 650-750 warm idle and it is anywhere between 60 and 45 when driving depending on temp and how many miles are on the oil.

No I don't think I have an oil cooler because I recently added a transmission cooler and my mechanic offered to add an oil cooler too but I didn't want to relocate the oil filter. As I said before, I'm not concerned about the oil pressure fluctuating between 20-60 psi. I know that'* normal. What I am concerned is when it drops to below 10 psi at idle when the engine is hot. The last week it'* been dropping to almost zero when I stop at a light and I have to put it in park and rev the engine.

Below 10 psi is bad news. But so is 235 degrees. I think our radiator fans are programmed not to turn on until something ridiculously hot, like 220 or 225. That may be OK for a new car, with tight bearings and a new cooling system, but when you get older and things loosen up, that high temperature is gonna contribute strongly to the low oil pressure you are seeing.

What is the oil pressure at idle when the engine temperature is below 200 degrees?

If it is near normal, I would hasten to replace the thermostat with something lower, even a drilled 180 like I have in mine. You want to keep the normal operating temperature below 200 degrees. You may have other cooling system issues like a plugged up radiator or a weak water pump.

Damn............Ya I'd be a little worried about that.