For starters I should ask, you do have an auto trans right? If so follow the steps in this link. He drops the pan and does a really complete cleaning job of it but you don't have to. Skip down to step 37 and start there.
Dropping Pan And Flushing Transmission
These transmissions take Dexron III or better. I usually use Valvoline Maxlife Dex/Merc or Dexron VI. Both of these are synethic blends. The Maxlife is very inexpensive and seems to be good stuff so I usually get that.