http://www1.autozone.com/servlet/UiB...3d801522d5.jsp
This link takes you directly to the Renix sensors but you can navigate to other systems as well. You'll find the testing and replacement procedures for all of the sensors. Just go through them one by one. You can't just "disconnect" because some are needed to start/run the engine. Bookmark this page for future reference.
You can find DRB II scanners on eBay for much less but getting them paired with the right cartidges can be a challenge. In the end, they only read the values at the diag ports which you can do with a DVM.
You should also get a Chiltons or Haynes manual and download the FSM from links previously provided.
With all of this, you'll find the answers to a lot of your future questions.