How may a non-mechanic replace oxygen sensors on a Mazda MX/3? on 1993 Mazda MX-3

My 1993 MX-3 failed the low idle hydrocarbons test at the DMV. Can anyone help me with this problem?
(I am unemployed and cannot afford the $800 estimate that a garage gave me to replace the spark plugs and the oxygen sensors. I was told they needed to be replaced due to oil leakage.)

Thank you, very much.

Asked by for the 1993 Mazda MX-3
FIRST THING to do BEFORE spending any mony on car is to educate yourself on the emissions laws!!!! Find out if they allow a 'waiver' if , after you spend a certain amount , it still doesn't pass emissions. Find out how they require the repairs to be 'documented' etc. DEQ , or DMV online in your state may have some info.