Today is going to be fun. Your ride takes you north out of Gunnison on CO 135 alongside the Taylor River.
On the east side of Cottonwood Pass you'll be on County Road 306, which is paved, and which loses 4180 feet in elevation over 20 miles. Should make for a great descent. If the weather gods can grant you one day of dry, mild conditions, this would be the day. The unpaved portion on the climb won't be bad if it's dry, and the descent will be so much more fun.
The end of your 69 miles will bring you into Buena Vista, in the high mountain desert of the Upper Arkansas River Valley. Grab a sandwich and shake at K's Dairy Delite and lounge along Cottonwood Creek in McPhelemy Park. You'll have earned a good night's rest, and you'll need it for a big century day tomorrow.