How to create new units?

I guess this has been asked before, but here goes anyway...

I want to create a new unit. A mix between the triarii and the legionary cohort. A legionary cohort, but with spears and with the post-marian shields and helmets, and perhaps the testudo-ability.

I tried a few months ago (can't remember exactly what I did) with v.1.1 but I had a few problems. The unit looked like legionary cohorts, with their normal weapons, instead of spears (I changed in the unit desciption file so that they had spears and tried to change a few other files (texture-related I think), but obviously I failed). Also, the unit looked like peasants in the recruitment window and on the small picture in battles.

Anyway, my question is: how can I create this unit? Which files should I edit or create?

Have you seen GodsPetMonkey's unit editor in the guides. This tool is excellent for editing unit stats.

About the units not getting their spears. To edit what weapons the unit has, you need to edit the 3D model. For this you need 3dsmax which costs a bomb.

To 'gray peasant' in the bottom is because you didn't give your unit a unit card.
Have a look at the Edit unit cards section here: Some How To's

If this still isn't clear, I'll try to post in more detail...