Trackplan
Ok, here is my first attempt at this track plan. Where should I start

! The red and blue lines are the two mainlines the blue travels counter clockwise while the red travels clockwise. (Keep in mind, that obviously the curves aren't all quite to scale.)
The yellow is the branch line that grades down and into a helix to a staging yard underneith the layout.
The green line is another branch line and breaks off from the yellow and runs about 4 inches or so below the top of the main layout. This line is going to be 18" radius and will serve a lumber mill that will be at the end of the peninsula where the green line stops. I am planning to have about one or maybe two feet on the end of the peninsula for that. I am not sure exactly yet how I am going to set that up.
Oh ya! And the red (or pinkish) squares are places that are untouchable, besides the space allowed for the main lines. The top box is probably going to have a small town and a precious minerals mine. The bottom box is going to have a flour mill and grain silos, but those sections are specifically marked off for other individuals so I cannot touch them.
The lower peninsula where the yellow branch line is, is going to have a mountain, and scenery to the floor. Then behind the mountain and over to the yard is going to be city, and industries. Obviously I don't know how I am going to have that either. The upper peninsula will also have a small town with a couple of industries, it all depends on what can fit there.
Now as for the roundhouse and whatnot, I am not sure exactly how to arrange things there, I want it to be able to service both diesel and steam. Should I have the turntable accessible from the main line in the two places or should I just have it single access? Like I said, I am not sure how things are supposed to be done.
I don't know what else to explain so please ask questions!
Thanks Freelancer