You need to read all the links in below in my signature.
Note to the wise: 02 sensor and MAF replacement should be the LAST thing considered and performed. You will likely have plenty of other problems to address before you get sensor replacement!
If you are using anything other than a computer, you will not see the links in a signature, smart phone apps do not display signatures.
You can have all the tools in the world, but our eyes and your brain are the best diagnostic tools available.
The good news is most of the obvious problems are well documented and can easily be visually inspected.