There are 14 LDD files that split up the Sandcrawler in smaler units.
I've used these files to build the Sandcrawler. Without them it would have been impossible.
If you want to build your own, you'll need knowledge of the LDD program.
The interior is mostly DBG or LBG and some Reddish Brown. While building I did not take in account that some parts are rare in a particular color. So I used old brown and some dark brown too. The result was even better as you get this worn and rusty sight of the Sandcrawler.
There are also dark orange parts. Using orange or dark flesh also works well as some dark orange parts are difficult to find.
The gear parts in the wheel units (4x same) are in yellow. This is a rare color, but you can switch them by the cheaper and less visible black ones.
All red, yellow , purple parts can be replaced by any color as these parts are inside , hidden in the structure.