Glad to be here,,, my question is ,,would anyone buy a o2 sensor on eBay,, i just dont see how they can sell them so much cheaper than a parts store,, ,,

 

As long as it is brand new and it's an AC Delco or Delphi, sure, eBay, Amazon, RockAuto, no problem.

Some of these vendors can undersell a parts store for the simple fact they don't have a brick-n-mortar store front to maintain. Many of these eBay businesses don't even have any inventory (you make the order and it becomes an order through a connected wholesaler).

 

^^ I second maniac's post.