+1 on getting your bike fitted. It makes a huge difference.

I think you can do it. Be sure you're eating well and that you bring something for electrolyte replacement. I learned the hard way that electrolyte depletion hurts. Bad.

At the very least, SmartWater, but I can recommend GU2O and these yummy little Luna chewy things. They're like gummy bears, but they have nutrition for women who exercise for long periods. I like the taste, anyway, and they sit better than heavy food.

Good luck with your training!

Roxy