I ride with my Canon 1D in my Tamarac Top Loader straped to my chest all the time. This is a great way to have access to the camera at a moments notice and is quite comfortable.
I ride a Suzuki 400SM and travel tons of back roads and double track trails and have never had a problem with the camera or the pack. One way to get around bringing so much gear would be to bring a good size CF Card, and then bring one of the hard drives that can accept the CF Card. This would free up the lap top and lots of cords. I know Epson has just come out with an 80 gig model that has a nice size screen and would be a great way to transfer the pictures off the card, and keep it seperate for securtiy.
SOunds like one hell of a trip, I wouldnt waste your time with the hassle of lugging film around for a trip of that length. When every ounce counts, you'll save a ton of weight with a good digital set-up.