Mario Kart Double Dash: Luigi's Mansion

So I got the model and turned it into a map. Here’s what I have right now:

As you can obviously see some of the textures are completely see through. I used wallworm in 3DS max to extract them and everything but for some reason some parts are still pooped out. Any idea how I can fix this?
EDIT: Got the transparency issue fixes, now I have two more issues.

Besides the still issued textures I need to make the map (which is actually a whole model) solid. How would I go about that? Also it’s gigantic so I need it to be scaled down. How would I do that in hammer?

As in making the thing solid, you mean the model doesn’t have collisions?
I think you would be better off making the basic geometry from brushes, and split up the model in individual detail models, such as the chimneys.

Right now I’m remaking Luigi’s Mansion as well using all the original textures, and I found out Hammer simply doesn’t like those chimneys.

@Merijn, build them up with triangles instead of skewed rectangles.

prob because faces must be convex. you can go into vertex mode, select vertices and hit ctrl+f to manually split it into triangles. (useful for getting convex meshes)