Don't be intimiated as your have got a ton of time.
I have met people on tour who are using dept store bikes and have 1 set of clothes and a tarp & sheet strapped to their rear rack and were having a blast and others with literally $10k worth of customized bike & gear who weren't as happy since some things were not going as they had planned.
Point is don't over plan as on any long trip, it never stays as planned. A lot of the learing can be OTJ training if need be, i.e. look for rocks and roots BEFORE you setup your tent so when you finally go to bed your back is not being stuck. Obviously, the advice others gave is quite valid but be sure to not fret too much if your aren't 100% ready. You can always take another day on tour if need be since your are retired you lucky guy!
Since it sounds like this is your first trip like this, perhaps you might consider buying high quality used equipment in case touring is not your cup of tea.
Also, depending on your route & distance per day, you might arrive in the Rockies a tad early as snow can melt late there. After you get your draft route planned out, you can an idea of how long it will take you to reach the passes and then find out if they are typically open by then.
My best advice is to start off with a properly sized/tuned bike and know how to do at least minimal repairs, i.e. change a flat/tire, adjust brakes & gears, and adjust seat and handlebars.
Also, don't overpack. If the item can not do at least 2 functions, do not take it unless CRITICAL such as a stove. Do you really need that pillow or can just some balled up clothes work in a pillowcase (doubles as a laundry bag)?
As Jim said, crazyguy is a great site so you can research/ask questions there also. Read the journals to get an idea of problems they may have had to learn from their lessons.
Most of all, enjoy the ride!!
Happy trails and may the wind be at your back!