The long trip is a good test. You'll know if it's right for you. We loved it so we took the plunge.
Start by sorting everything in categories: 1. Trash. 2. Give to family or friends 3. Have one huge sale 3. Donate the rest.
I would not store anything unless your kids aren't old enough to have their own place. If they aren't, I would ask them what they want stored. Most of the time when you ask them, they don't want it either. We did store 5 plastic sealed bins of old photos and momentos that we couldn't part with. They are in our daughter's garage. They will mean more to her later on.
Sell the house. It's freedom you want and having to maintain and worry about a home isn't for us. We have no regrets in that area.
Figure out what you will do with the mail. Our daughter forwards ours. We buy the prepaid envelopes. Meanwhile, stop all junk mail, magazines and catalogs.
Make a plan and start checking things off. We have been full timing for 5 years and have no plans to stop until we're too old. Then we'll worry about what to do next. You should think about what that would be.