I never played a GOTM in the past but I remember that with Civ III people needed to provide saves of their games at specific dates (1000 BC, 1AD, 1000 AD etc.. not sure what they were)

For this GOTM, do we need to provide only the final savegame and/or the replay file?

AT the moment, yes - final save & replay. We'll work out what's needed later, but we encourage people to keep a few other saves as well. :)

How you make a replay file. ?
And is a screenshot also required ?

Screenshot is not required. Replays are made automatically as you play (look in the 'replays' directory.

Forgive the newb question, its my first post. How do I use a replay myself - I assume it just shows you the final stats session?

Answered my own question, shows the final stats session. Just double click on it.

What about spoilers?

We still doing 1000BC or later as the game takes longer to get steaming. 1AD maybe?