91 Prelude ECU code

I have always had my check engine light on my lude since i bought it. i checked it today and it was a code 41(Four delayed blinks followed by one quick blink = 41 right). I researched it a little and found it to be an O2 sensor heater. what is an O2 sensor heater? how important is it to engine function? and how do I replace it? Anyone who can help please do i'd much appreciate it.

:silly2:

by the way, if anyone can tell me how to read the ABS codes that would be helpful also. Thanks.