Check engine light

So my check engine light has been on in my truck for over 9 months. I decide to fix it over the pass couple of days. I bought a air filter, O2 sensor, and spark plugs. I got four of the eight spark plugs in. My O2 sensor is not coming out easy. So tomorrow I am driving to work in Kyles truck(one of my best friends). Then when I get off I am going to try to finish fixing my Truck. Gong to see Emalie this weekend I am STOCKED!!!  Peace out