fluid is personal choice. i prefer synthetics (Redline D4 for me).
when changing fluid, the first plug to remove is the fill plug (the higher one). if you cant get it out, you dont want to drain your old fluid. a 3/8" ratchet wrench fits in the plugs to loosen them.
i prefer to use a length of clear hose and a funnel to fill the trans from the engine bay. some remove the tranny shifter and fill from there (fill till fluid comes out the fill plug). some use pumps from beneath the car. just whatever works for you.
good luck.