You need to look at TechTree_Trog and Techs_Trog (or Techs_Amarian depending on faction allegiance). Look for these files in the Only-SP folder. Then most of the buildings are in EmpireSpecialImprovements for empire, yada yada. Look in the Core Improvements folder. The improvements are spread out amongst a few different xmls, but they are all in that folder. What I did to make my race have completely different improvements was to take the original starting buildings (I used empire, so labor pit, archivists, etc) and prereq them to the race of fallen. (All empire factions have been set to the fallen race). Make sure in your raceconfig file that you have the <RaceClassification> set to your race name. I think there's another file you have to edit for that as well. I believe it's Racetypes. If you want, check out my wip mod here:
I'll be uploading an update later, as I had to fix the spells since 1.08 came out.
At least if you check all that out, you can get an idea of what I did.