Oxygen sensor troubles

Im not sure if this is the correct place for this but I need some help. Im not very mechanically inclined but my friend is trying to help me with that so if my description sounds off im sorry.

I just bought a 2003 Toyota tacoma prerunner 2.7 engine. My check engine light came on and I took it to be read. It was a p0135 code and the guy said it'd be my oxygen sensor. Took it to my friend to fix it and he did but one of the nuts broke. Took it to a shop, they replaced the nut and bolt. I told them to clear the code which they did but it came right back on. They checked it and they said something about the wiring and heating component i dont know. My friend spliced the wires to the new oxygen sensor because the female male connectors would not fit so he took the old connector and put the new wires through it.

I guess my question is how easy of a fix is this? Also my friends are telling me I should have 2 oxygen sensors but I only see one. How many does my truck have? Thank you for your help!

 

Your truck should have two. The first one is a air/fuel sensor and the second is a 02 sensor. Crawl under your truck and look.

I would buy factory replacement denso units from rockauto.com. Dont mess with those universal units.

 

I just replace my upstream O2 sensor in my 01 Tacoma after getting a P0135 code at Autozone. It took me no more than 15min to change. My truck runs noticeably better. My only question is how do I clear the code to get the CEL to go out?
By the way, go to Rock Auto for the sensor. They have the best price. Toyota wanted $234 for theirs. I got mine for about $130 with overnight shipping.