Tan,
If you have the Tremec Trans, which I'm sure you do, there is two plugs on the passenger side of the trans. One to drain it, and one to fill it. The top one is obviously to fill and check the level.
You will hear about all kinds of different oils you can use. I use the recommended Synchromesh
oil from Cheby( GM). I know you can get some different types at Goodies or even off the Performance Unlimited site.
Scott