Emissions Question

Hi

I just had my 1989 300se inspected for the first time.

I replaced the air filter,oil change, and plugs.

The car just barely made it through the dyno test.

HC Limit 2.00 reading=1.43
CO Limit30.00 reading=26.77
nox Limit 3.00reading =0.75

The tech suggested the O2 sensor be replaced .He also stated these should be replaced every 30 k miles.
Does this sound right to any of you???

Hope someone out there can shed some light on this.
Thanks

Razorman

P/s Im in trouble now, no spell chack LOL