Where do I start?

[Rodion Romanovich]

I want to create a total conversion mod. Factions, map, units, buildings and wonders will be changed, as well as senate changed into a new faction, and victory conditions being changed. Models and animations probably don't have to be changed (perhaps good in some cases, but not necessary), What's the best thing to start modifying first?

I reckon changing units now would mean linking them to a faction but won't I then have to do a lot of new work in order to change to correct factions when I change faction names etc. afterwards? Or if I change factions first, can I test run anything until I've fixed all units etc.? My question is basically in what end I should start if I want to be able to complete the mod as quickly as possible with as little effort as possible.

(And it wouldn't hurt if some experienced modders joined my team too...)