If you have never done a long day on the bike, you might want to take one of your days off and load it like you want to for the trip.
Ride out for what you think will be half a day (5 hours most times maybe 6), then turn around and go home, look at your odo, that will be about average.
Plan to stop every 90 to 100 miles, or if you like every hour and a half, walk around take a leak, stretch.
I rested when I felt I needed to, made the breaks short (10-15min) and walked most of it.
Get you a good pad to put on the seat, you will need it.
When I went up to North Carolina from Florida (800 miles), I broke it up into two days, I rode 600 one day and 200 next. Only did that because I wanted to take it easy, after the dragon run, I drove all the way home in one shot, took me 12 hours do go the 800+ miles, and that was mostly interstate (course I had a bad back).
Long trips are really no problem if you stop when you feel a little sore, and eat when you are hungry.
Start slow and see how you feel, you might actually get doing longer and longer stints between breaks.
Good luck on your trip