There is a specific troubleshooting flowchart for each automatic transmission. Driving a car with a malfunctioning automatic transmission is a sure way to kill the transmission. Park it immediately until you can run it through the tests to see if it is salvageable.

If you have made up your mind that you won't get your transmission fixed and will replace it then you can't loose anything with the trans-x.

There are individual books for each transmission called tech guides, I don't remember the name of the company that sells them. The tech guides usually sell for $15 or so. There are other professional manuals like Mitchell that you may gain access to.