A good backdrop can make or break a scene. Kudos for your initiative.
If you can make two trips, all the better. By that I mean your first attempt will have some slight errors in it. The lighting direction may be wrong, the camera lense may roll down by a couple of degrees as you take the photos.
Photoshop is ideal for this, but even a basic stitching program from Canon suffices.
Check focal length. You want something around 100mm. Don't got below 50mm, 35mm at most as the images will be wide angle, and the stitched horizontal lines won't be flat. Bump bump bump.
I include around 10 photos... this depends on the resolution of the camera (mine is an old Nikon D70s 6MP). Experiment!
A tripod is a must.
A spirit level on the hotshoe will minimise a downward sloping image
Make sure you have enough sky in the frame, otherwise you may need to reshoot. If it's a bright blue sky with no cloud, PS can be used to extend the top of the sky.
Here's one I took of Mansfield. http://www.mansfield76.webs.com
(here you see only about 3m of it across)
It's 10m long, but only 0.5m high, and I would have preferred a greater ratio of sky to hills in the final image, but overall it will work.
Then print out the photos in B&W just to get the scale correct relative to the modelled area. The biggest limitation with photo backdrops, or biggest opportunity for greatness! is the viewing height difference between your viewing height and the height at which the photo was taken. These will be equal at some height, so before selecting whether you want to shoot down on or up to your subject matter, decide on your layout height.
Photobackdrops look great in the magazines, as the layout (with backscene) has been photographed at the optimal position in x,y,z for that specific backscene.
Once you are happy with the digital image, find a cost effective printing company.
BTW, I took the photos that formed the 2nd series of backscenes from Hobbies Plus.