Since much valuable advice was given here I thought I owe an update on my first century at "Hotter N Hell 100'. I got it done, yay!! albeit at a slower pace than what I was hoping for.
100.88 miles, 1165 ft elevation gain, 6:43 moving time, 15 mph average, avg heart rate was 151 (my resting HR is in low 60s). It was moderately hot for Texas, it got into low 90's by the end of the ride, but was manageable.
Most of the advice here worked well; I paced my self well through out the ride, kept note of physical comfort by changing positions (saddle, hands, neck and shoulders) and took my shoes off at all breaks. Was able to get good drafting in the first 30 miles (was averaging 19 mph at the mile 30 rest stop) but the rest was mostly solo except for a couple miles here or there, kept an eye on nutrition at rest stops (stuck to bananas and the dates I brought with me, zero gels which I think I will need for the next ride), hydrated well during the ride, specially around the end.
Next century coming up in 4 weeks in Arkansas in a hilly terrain. Training for that starts this weekend.