Mirror - it'll save your life.
Very low gearing ratios
Good luck I love my Surly LHT - just about to take into the hills of Wales
My wife and I just returned from a month touring those hills and more on our new LHTs!!!
To the OP...
If you get the medium sized Ortleib handlebar bag, just get the map case that goes with it. If you are carrying camping gear and riding solo, plan for front and rear bags. It's always nice to have room for groceries when camping is miles beyond the last store.
We chose the SKS thermoplastic? fenders and Tubus Cargo and Duo racks. The Duo is nice if you are packing and shipping your bike since they are small and independent.
Good call on checking with LBS on sizing. I've ridden 56 cm c-c road and touring bikes for over 30 years and ended up buying a 54 cm LHT with 26" wheels. The 56 was too stretched out to be comfortable very long.
Personally, I think the 700 vs 26 arguments are mostly blowing smoke, equivalent to mental masturbation. For most of us, touring will happen within easy reach of UPS/DHL/FedEx, not east of Ulan Bator, so replacement parts will be reasonably available in a short time. I'm using 2.0 Marathon Supremes and my wife still has the stock 1.6 Conti's on them.
Of course, YMMV.
Jay Peterberger Bike Adventures