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

What is your question?

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. Roger