1997 Integra LS

Well, i have the similar knocking and strange jumping idles I was reading about, which is apparnetly caused by the o2 sensor. Can anyone tell me the location or post a diagram of it?

I also went and go an oil change on my car today and they said my drive belt was about through and would need a new one soon. Then proceeded to go into a story of how for timing belt, drive belt, and new water pump would only be $499. I def. don't have that money right now, so i think I'll replace the drive belt myself. Anyone have input to how difficult this may be or any tips I should know beforehand?

Also, I site or shop with good pricing for either the o2 sensor or drive belt would be much appreciated, thanks!