I have a 2001 RX300 w/ 96,000 miles on it. My check-engine, VSC and TRAC control lights came on. My local mechanic (non-Lexus dealer) said my front A/F sensor (similar to oxygen sensor) is bad and needs to be replaced. He says it will cost about $375 for the part, labor, tax, etc. This seems somewhat high, since the part shouldn't cost more than $250 - is this worth over $100 in labor?