2000 Galant Transmission

I am trying to change the AT filter on my 2000 Galant. I have a Haynes manual and it looks fairly simple. When I get under the car though, I see that the Haynes description and what I have is not the same. On mine it appears that I do not have a drain plug and the transaxle pan is mounted vertically rather than horizontally as shown in the Haynes. Do I just remove the pan bolts and let the fluid drip out in a mess to replace it? The Haynes also says the unit needs 8.5 quarts of fluid. Autozone tells me 3.5. Which is it? And the book tells me to use Mercon fluid. My journey through this forum seems to say that I should use fluid from the dealership. Is that true? Any help would be appreciated. You can email me at johnchambeatearthlinkdotnet of you prefer.