Patrick,
welcome to the OGR Forum. Assuming you have the personal side of things well in hand - the forum is a great place for advice. I actually really like the track plan the Moonman put out. If you are using a Polar Express to climb hills it needs to be one of the recent offerings with the handheld remote known as Lion Chief or Lionchief Plus. The very early transformer only offerings were too underpowered to reliably climb hills.
One option for you would be RR in a box. They are a forum sponsor. I have seen there products but not used them. If you want something with elevation changes you can assemble in a hurry and still look nice its probably a good option. As others said above, you will still need considerable time to to decorate things.
Good luck
