It's time for a different mechanic who has better communication skills; (something that's rare). You have multiple things going on that should not be related. The crash and new radiator seem to be unrelated to anything. A defective alternator will cause the battery to run down while you're driving. You didn't say whether that "loss of power" was loss of electrical power or engine power. If you could still crank the engine, the alternator and battery were probably okay. A bad alternator and / or battery would have required the use of a jump-start with jumper cables or a battery charger at some point.
None of that would have anything to do with oil pressure, and if the pressure really was low, you would have seen the red warning light long before any serious damage occurred. Even if you have an oil pressure gauge on the dash that often fails to get our attention, there will be some type of "Check Gauges" warning light. Continuing to drive even a very short distance with no oil pressure can cause serious engine damage. The engine would last about as long as you would without blood pressure.
Black exhaust normally means too much unburned fuel. "Metal-on-metal" can mean and can be caused by a lot of different things, not all of them serious. Silicone gasket sealer in the oil pan is not unheard of and is rarely a problem unless it is there from a previous repair.
If the alternative to junking the car is buying a new one, I'd definitely spend whatever it takes to fix your current one. I can give you a five-page dissertation on why I drive an old rusty trusty '88 Grand Caravan every day and let my newer cars sit in the garage. This forum is full of people with expensive car problems related to all of the unnecessary technology the insane engineers are forcing on us.
Wednesday, December 28th, 2011 AT 1:23 AM