Yet More Mod Questions

[tinkthank]

Thanks much.
I tried reposting, but the boards were down.

My problem is this: I have found the right combination of starting sites with the right number of units, but I cannot find out how to change the #spr1 and the #spr2 command for these units.
I mean this:
Let's say I take the Keep of Ulm -- it gives me 2 units, one a commander and one not, as capital only recruitables and no gems, great. So I take their numbers, mod them, and I'm all set.
BUT: I cannot find the .tgas for the units I want to replace them with!! I wanted just fairly simple horseman types, so I took the Red Guard as an example, because I REALLY CANNOT make new unit graphics, it will look just so crappy. So I cannot find where to have the #spr1 and #spr2 commands lead to. So the mod will work, but instead of mounted horsemen, I get Guardian-looking units.
Do you see my problem?
Since I cannot actually change the graphics, I thought I would use the game's existing ones. This works fine as long as I can select a monster which looks all right to me. This works well -- except for the nation's capital-only units.
So where can I find the .tgas? I searched the whole folder, but I dont see them!