Hairline crack in the engine block or a blown head gasket?

An idealistic technology for a consumer population with unrealistic expectations. Ah! All I need to do is drop by PEP Boys, purchase the part and replace it. Right! I doubt if 1% of the North American populace can even touch anything under the hood of a 2003 model vehicle. Ideal? I imagine the quality of repair degrades from the garage door of the dealership to the back alley jack stands of a 'fly-by-night' mechanic. But, but, I can change the engine oil, or I can change the transmission fluid and pan gasket. The windsheild wipers look easy. Good! That is about all you can do.

If you are driving around with a faulty O2 sensor, would anyone stop you to point out your polluting habit? Next time you go grocery shopping, look for those oil markings on the parking lot pavement. While you're at it, run your finger on the inside of a few tailpipes too. Are they carbon black, oily soot or clean gray? When you drive home on that concrete four lane exspressway, please note the dark band in the center of the lane?

€sunblok€, did you know that all of these vehicles are not 2003 models. Some are 2002,2001,2000,...1980,...1970,...1969,.............models. Okay!

So what is so hard in removing and replacing the O2 sensor on a pre-catalytic converter or down-pipe of the exhaust?

regards,