Taking all the responses into consideration, I have a new plan. Although I the goal is still eventually to get a Surly, I'm going to aim lower for the moment. I'm looking for a used Kona Unit X, most of which have a rigid suspension corrected fork. It looks like they go for around $800, so I won't be breaking the bank, plus if I hate it, I can sell it for around what I paid. So it's a low risk way to get a feel for how a bike built for bikepacking rides (including the rigid fork). I can start making changes to fit my preferences (suspension fork, etc) once I've decided that a) I want to keep the bike b) the changes are actually warranted (maybe I'll learn to love the rigid fork?)
My big trip is in early August this year, so I have plenty of time to get things in order. In a departure from earlier trips, this one is mostly dirt roads with even a little single track. So I'll really get to put the bike through the paces.
Maybe in a few years I can get the Surly. Or maybe the experience with the Kona will send me in a completely different direction. Either way, thanks for all the help!