Replaced my o2 sensor - P1115

[Perfectlap]

I'm replacing pre-cat left this Saturday morning. Sensor arrived from oxygensensors.com $125 delivered two day Fedex.
Anyone have an exact photo or diagram of where the o2 sensors are? I've seen a few but pics but they aren't great.

[smartguys]

Hi Guys,

I wanted to be sure I didn't make a mistake.

I see you all are chatting about 02 Sensor readings/replacements. Dealer pulled code, and told me I need 2 sensors replaced. Parts and labor $640!!!!!!!! What a scam.

I bought 2 on ebay. Very cheap.

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=290234863051&ssPageName=ADME:X:RTQ:MOTORS:1123#ht_2808wt_0

They are not custom fit OEM, rather, one sensor fits all -- assuming splicing the wires to the old clip is a simple job.

Question #1: Are these ok to use? The ebay auto parts store, when asked, said yes, as did past customers. I want to be sure.

Question #2: Is there a photo diagram of the replacement process available somewhere that shows how to do this job?

Question #3: DO I NEED 4?

thanks
Kelly