Hello, considering my first Amtrak trip, from Omaha to Denver/return on California Zephyr (5 & 6).

Since it's overnight both ways, I'm considering a Superliner Roomette. Do these sleeping cars have a central hallway with rooms on both sides, or a left/right hallway with rooms on one side? Also, can you pre-reserve a specific room or side of the train?

I would be taking a GPS, and would prefer a south-side upper level room for GPS reception purposes. Location on train would be important.

Everything else I needed to know is on Amtrak's site (power, room pictures, etc, but I can't tell from the Quicktime VRs the positioning of the room vs. the hallways).

Thanks
Jim