>>>>Step 1. Borrow some touring gear (a couple panniers, a tent, a sleeping bag) and do an overnight tour.<<<

I agree. I remember being so excited about getting back into cycling 18 years ago that all I wanted to do that first year was start planning my first trip around the world. My first trip around the county cured that, fast.

The most I've done at this point is a five-day ride through three states, but that took a few years of shorter trips as preparation. Congratulations on losing 100 pounds. That added a few years to your life. Use them for overnight rides and learn all you need to learn before heading out on the "big one."