Excellent question. I'm sure the responses will be well thought out and all over the place.
My 2 cents....Keep your daily mileages reasonable, error on the low side at first. Just because you've ridden a century on your lean and mean road bike doesn't equate to riding when fully loaded. This and the fact that you're going to have to ride tomorrow and then the next day and so on..... pace yourself and leave a little in the tank for the next day.