Yea, that green line is kinds freaking out my eyes. It is a little distracting, I saw it then followed it to see here it went...
As far as resizing and stuff, start with displaying the rulers. Change the rulers to show inches or whatever you're comfortable with. Then set up guides and created a box the size you want.
The next thing to do (Which I just learned from Stingray, thanks

) is to "Scale Stroke Weight". Go to File > Preferences > General, then put a check in the box next to "Scale Stroke Weight".
This will keep the lines you've drawn to the right scale. Otherwise they will become thinner if you increase the scale and fatter if you decrease.
After all that make sure everything is unlocked, then select all. You can then resize by holding down the shift key and clicking and dragging a corner. This keeps everything at the same scale.
You can then modify as needed to fit your box.
Hope this helps
Bob