1998 Chevy Blazer w/60k miles dying while idling - please help!!!

I have a 1998 Chevy Blazer and it's been dying on me. It only has 60,000 miles on it! I am so disappointed. Here's the situation.
1. It first died after driving about one hour on the highway at
70mph. While it was coasting, I put it in neutral and restarted it. It restarted with no problems. The engine light came on right before it died, but no warning lights have come on since. The engine light has never come on again.
2. Now, my Blazer dies after I drive it for about ten minutes. I put it in park and then wait about 30 seconds and it just dies.
3. While I am driving it, it makes a very strange sound. It reminds me of the noise that you hear at car shops when they are removing tires. Kind of an electrical zzzz......zzzzz sound.
So we have taken our car to three different repair places in the following order.
1. Chevy dealer - wanted to replace lower intake gasket, valve cooler gasket, lifters, water pump. Estimated cost: $2000. I thought the estimate was too high and did not trust the dealership so we left. We paid $70 for the estimate.
2. Small Local repair shop - For $206, they replaced the belt tensioner, fuel filter, 1 head gasket chemical, and changed the oil. This did not repair the problem. But this shop ruled out the water pump that the Chevy dealer wanted to replace.
3. Larger chain repair shop - We went to this third shop, after the car started dying after 10 minutes of driving and putting it in park. Now, it makes the weird sound that makes me afraid to drive it. This shop wanted to replace the control module and ignition coil for $580.00. (Diagnostics run by this shop and the Chevy dealer did not reveal anything.)
Can someone please, please help me??? I can't afford to put any more money into this car unless absolutely necessary.
What do you think is wrong? Is it the control module and ignition coil? Is $580 a fair price?
Thank you in advance for your help! I appreciate your time.
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Did any of these shops look at the computer with an OBDII tester? Even though the ses light goes out the codes are still in the computer. Are you loosing antifreeze? This would be an indication of a lower intake manifold leak which is common for GM v6's. If it is leaking into the engine it will shortly destroy the engine. Unless you are going to take on the task of learning how to troubleshoot the problems you need to find someone you trust and work with them until it is fixed. Any WAG's you get here will just cost you money unless you have the skills to determine whether it is a problem or not. Someone with the skills to use an OBDII scanner is needed to analyze it...

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