Fun & Fitness over 50

I read a lot about training and cycling. Currently I am reading for the second time, Bike for Life: How to Ride to 100 by Roy Wallack and Bill Katovsky and also The Heart Rate Monitor Book for Outdoor and Indoor Cyclists by Sally Edwards and Sally Reed while also working my way through The Cyclist's Training Bible by Joe Friel. The problem with that is that I can get overwhelmed with information. It's not that they contradict each other it's just that there are as many different approaches to training and fitness as there are people on the planet! Also, as is the case with the Wallack and Katovsky book, there are many interviews and case studies of actual athletes who are extraordinary. I guess it's intended to be inspiring, and it is, but for me it can be discouraging too. I get feeling pretty good about myself for hitting 20 mph at 85% MHR on Meads Lane and then read about an over 90 guy, John Sinibaldi, who can still hit 35mph on the flats and sustain it for miles and miles.
The other day I was looking for local races and found a club site that listed some. One race was 75 miles. That's 75 miles racing, as in, ALL-OUT-EFFORT. I'm just hoping to get through 62.5 miles next Sunday at the Tour de Cure without being pulled from the course for exceeding the cutoff time.
My expectation is to ride with the big boys and I'm certainly not there yet. The perspective I'm trying to keep, while staying motivated to set ambitious goals, is, even if I finish dead last with everyone drumming their fingers waiting for me to come in, that's better than the ones that could have finished but didn't enter out of fear or lack of motivation or those that aren't even getting up off the couch.