96 Oxygen Sensor?

My neighbor needs some help with his 96 Explorer (4 liter engine). The check engine light is on and it idles rough. I think it needs an oxygen sensor (according to Jiffy lube) and I was wondering if there is more than 1 sensor. I assume this is a relatively easy job but I don't have a manual for this vehicle (it's not mine). Is the sensor on the rear of the engine where I need to put the vehicle up on ramps? Any special tools needed?

Concerning the rough idling, I think that fuel injection cleaner added to the gas would help. What do you think? Thanks in advance for your help!

Don't assume it's anything until you have the codes pulled. The code will tell you what circuit has the problem. No need throwing parts at it until it's fixed when you could replace one part(or sometimes no part is needed). Post the codes here when you get them. Remember, autozone scans codes for free..

My neighbor needs some help with his 96 Explorer (4 liter engine). The check engine light is on and it idles rough. I think it needs an oxygen sensor (according to Jiffy lube) and I was wondering if there is more than 1 sensor. I assume this is a relatively easy job but I don't have a manual for this vehicle (it's not mine). Is the sensor on the rear of the engine where I need to put the vehicle up on ramps? Any special tools needed?

Concerning the rough idling, I think that fuel injection cleaner added to the gas would help. What do you think? Thanks in advance for your help!
most vehicles at least V6 engines have four o2 sensors one before the cat and one after. as far as your rough idle problem it could be a number of things, bad fuel quality, clogged injectors, with out a whole lot of info we can't really help you. does it do it all the time regardless of temp.? does it run rough at other engine speeds? do you have the check engine light on?