There are lots of MS rides going on now. I'm getting ready to do a two day one myself in New Bern this weekend.
The rides are so well supported with frequent rest stops, so you will get plenty of opportunities to get out of the saddle for a few minutes. Take advantage of them and take in some nutrition at every stop. They always have snacks, water and gatorade. I definitely eat and drink their stuff, but take some of my own as well just in case they don't have anything that appeals to me. On the MS ride I do the stops are generally about 13 miles apart, so I try to finish a bottle of whatever I'm drinking between every stop.
The adrenaline will get you a good portion of the way there. If you can do some back to back rides between now and then, you'll do fine. We are planning on doing 75 miles each day, but a lot depends on the weather. The first year we planned on that, and the weather was so miserably hot we only did 30 miles the 2nd day. Last year the weather was beautiful, and we did our first century the first day and then 30 the second, so we try to stay flexible.
You will have a blast! The MS 150 is my favorite bike event of the year, and for such a good cause.
Lori
Grits
2010 Trek 5.2 Madone WSD, SI Diva Gel Flow
2002 Terry Classic, Terry Liberator