LOL! Gold rule #1: "Never, ever, EVER minimize Takedown Editor"
No, I'm not replacing any textures or materials inside the Editor, I guess is time for me to contribute with a walkthrough:
1. Inside Content Browser create a New Package: Clicking on the '
NEW' button at bottom-left corner of the Content Browser. I created it in: TakedownGame > Content. (Don't know if location has something to do).
2. Imported the image file for the texture into the newly created package. [ ABOUT IMPORTING THE FILE: Clic on the
IMPORT button at the left-bottom corner of the Content Browser and select the file from your HDD. [ ABOUT THE IMAGE FILE: Is a 1024x1024 .tga created with Adobe Photoshop: Save As > Type:Targa (*.TGA) ]
3.On the Import Dialog that opens up, make sure the Package name corresponds to the newly created Package and asign a Name to the Texture, also Grouping field adds like a Tag for organization (optional). The options below leave it like this (default) since this will be the texture for the diffuse map, and clic OK.
3.Once we have our texture imported inside the package, lets create the new material inside the same package too. Right Clic on an empty space > New Material. Again, check the Package name, add a Grouping tag, and a Name for the Material and clic OK.
4. The Material Editor opens up. Having the recently imported texture file selected on the Content Browser, go to the viewport section of the Material Editor and Hold T+Clic to create a "Texture Sample" element and join the black node of the 'Texture Sample' box to the 'Diffuse' node as seen on the image and clic the
green Check Icon at the top left of the Material Editor and close the Material Editor.
5. In the Content Browser, Right-Clic on the created Package now containing a Material and a texture and clic on Save (In the image is seen as 'Guardar' since my OS is in spanish. (IMPORTANT)
6. From the Content Browser Clic and drag the new material to the desired BSPs.
7. Close Content Browser, Build All, Save, Cook, Copy&Paste, Run.
That should be it. Hope I got it clear and hope it works for you too! Please keep me posted how it went!
Didn't run on any of the errors you posted!