replacing textures for buildings and doors

So, i am currently making skins for a Local sheriff dept to be used in GTA5. I wanted to go a step further and change out the sheriff signs and flags on the buildings to be more realistic.

I have the location of the textures for teh sheriff station in Sandy Shores (can't find the flag texture yet,anyone know where this is located?)

I have recreated the texture in Photoshop and imported to the correct location in OpenIV. This didn't change anything for me so i started looking some more. I opened the model file for the door and found it linking to another texture, a 256x256 texture not the 512x512 in the other file. So i exported all the textures for this model and opened the correct one into PS and added my textures to it and went to go save it to import it back in, but i dont know what the settings should be for a DDS file. I look at the 3d preview as I save it and it looks messed up. My text colors are combined and distorted, the badge has black behind it.

Has anyone edited these textures before or know which settings r needed for dds?

Thanks for the help