You can also look at HO plans and scale them down. A 36" x 80" hollow-core door is the equivalent of 6' x 13' or so in HO. I recommend not skimping on width... Going the full 36" gives you upwards of a 16" radius curve on the ends to handle virtually all N scale equipment.
HCD (hollow-core door) layouts can be limiting in that they're not the most efficient use of a spare room. Cockpit designs are more efficient. However, HCD layouts shine in portability. Case in point: I move every 2-3 years with the military so I never know what size or shape room I'll have at the next assignment. The HCD can fit in all but the tiniest rooms with little difficulty. Plus, they're just so darned easy to build and self-contained.
Best of luck! There are lots of great HCD layouts out there. Or design your own. I don't much care for the appearance of Kato Unitrack, but since it's so easy to work with, it may be worth picking some up (if you have the cash to spare) just to mess around with different track configurations before committing to a plan.
For actual track laying, I would recommend trying Atlas' code 55 track. Here's a comparison. I laid the main door layout with code 80 Atlas track:
But later, when I extended the layout, I went with the new code 55. I found it's just as reliable and even easier to work with, but looks much better:
Here's where I connected the two:
Code 80 on the left, code 55 on the right, both from Atlas.