I am fortunate to be able to bike a lot around the city as I don't own a car. My bike IS my car. I shop, do errands, go to work, and enjoy the ride! But I also know that biking long distance is WAY different then biking around town, even if bike is fully loaded with groceries.
Yesterday, despited feeling tired because of sinuses..I biked a bit further out on the borders of the city. Even though I recently adjusted my handlebar's angle (Hybrids come with special adjustment mechanism under handlebars, and you only need an allen wrench to adjust it), I found my back was getting sore. I will move it to the highest level it can go and try that out on a longer ride. If that doesn't work, I'll ask the shop if the handlebar can be raised. I also lowered my seat a bit..as it still was a bit high. Hopefully this works. Normally not an issue, but if you spending 4 days covering 400+ kms you want to be as comfortable as possible.
I will do some runs, getting longer and longer to get used to it and to get stiffness out of my legs. A friend of mine who is riding across Canada on the Sear's Kids with Cancer Ride in September has invited me to go riding with her sometime...I'll have to take her up on the offer. She's done the tour many times, but can't this year because she wants to focus all her efforts on this cross Canada ride.