Okay... So I have downloaded programs, spent almost a day to read a tutorial: "http://simswiki.info/wiki.php?title=Tutorials:TS3_Basic_HowTo_Mesh_Guide" and worked on separating and recoloring the chinese city wall from the WA... and I just came to a point where it's just so overwhelming for me who's not a native speaker... Also, the object in the tutorial seems to have different types of image files from this wall file has and what this tutorial does to the object is different from what I'm trying to do with this wall so I'm kinda lost in the middle of the tutorial...
Can someone please help me with this?? Or maybe it's not possible from the beginning..?

So what I have been trying to do was cut off that highlighted areas from the inner wall and outer wall and recolor the roof and the wall from redish to the one in another pic...