should O2 sensor with 102k be replaced without code given

What is your question?

service engine light on intermittently; was told code was egr issue valve looked recently done? I've never replaced O2 car had 62k when I got it now has 102. wondering if new O2 would improve my horrible mileage and performance and pass smog test? ideally need intake replaced/gaskets. its plastic and leaks oil/coolant passages for egr clogged I'm sure but cannot afford now; need smog this week! will O2 help? REPLY ASAP