$500 to
diagnose
and install an O2 sensor
and to remove and unclog the EGR pipe on a 99.

In the ballpark?

 

IMO no f'in way. But if you cant do the work so you pay someone to do it for you, thats what you get.

$80 Napa O2 sensor + 30 minutes labor @ $65/hr = $112.50
That leaves $387.50 left which is about 6 hours of labor left.
I dont think it would take nearly 6 hours to clean the egr.

You know they are charging you top dollar on the O2, dubbing around with dumb stuff, and totally giving it to you.