one of my favorite pieces of advice i ever received for traveling was don't wait until you start getting uncomfortable to begin changing your riding position...i start stretching and flexing my quads, hams, glutes, back, etc. about 15 minutes into the ride and make sure to never stay in any one position too long...it keeps the blood flowing through your entire body instead of pooling and you won't feel nearly as sore and beat the next day
next, have fun on your ride...don't push it too long or hard especially since this is your first time riding that far...if you see something intriguing, take a couple minutes to pull over and look at it and you'll be surprised at how many times you've passed right by something interesting in a car without ever noticing it is there