Hi there naive, I'm writing from Down Unda, where we're visiting family. Welcome to the forum -- you've come to a good place, where people have a lot of knowledge & experience, and are good about sharing that. Sorry to hear about your folks' breakup, with your house lost in the undertow, but as the saying goes, one door closes and another opens, and you seem to have turned a problem into an opportunity.
There's a lot of good commentary & advice on your Sherpa, so I'll not duplicate that. Let me add a couple of observations:
1) First, there's a guy here in Oz, Graham Smith, who posts regularly on crazyguy, who's ridden his Sherpa far & wide, and has written about it on crazyguy. Graham also posts here now & again, as "Vintage tourer".
I ride a Raven-mit-Rohloff, which I bought 2013. As part of my research, I exchanged some emails with Graham. He was very complimentary towards Thorn bikes, saying that they're robust to the point of maybe being overbuilt for most purposes. Certainly he's taken his Sherpa across rough terrain in Oz.
I haven't tested my Raven in the same tough conditions, but it's robust and very comfortable, and does everything I ask of it.
2) I switched to a Rohloff after having a lot of adjustment problems with a variety of Shimano derailleurs over about 10 years on my Eclipse ti-framed touring bike. My difficulties (they were hassles and recurrent nuisances, no catastrophes) seem to have been uncommon -- certainly lots of other riders have had very good luck with Shimano and SRAM.
One thing I did learn from my decade of experience with derailleurs, is that I needed gearing for loaded touring that was lower than standard manufacturers' offerings, and often lower than that recommended by bike shops.
You might want to experiment a bit with different types of touring, to find out what you like best. Is it camping, and if so, lighter, or more loaded? The weight you carry, plus your fitness, and your preference for pottering or pushing it -- all these things affect, and are affected by, your gearing.
(There's a whole discussion about the range of gear-inches as a way of indicating the lowest to highest gearing on your bike. It can get quite involved, and a bit mind-boggling until you're familiar with it. Here's an online calculator -- you enter your front chainring and rear cogs info, plus your wheel diameter, and watch what happens, bemused, befuddled, and ultimately hooked:
http://www.gear-calculator.com/)
On my Eclipse, now a day-ride bike, I finally was using a 12-36 Shimano Deore cassette at the rear, with a 24-36-48 Deore triple at the front. That bike has 700c wheels, with 32mm tires. My lowest gear on the bike (24 at the front, 36 at the rear) was 18.5 gear-inches, if memory serves. I found that ratio just barely OK for climbing a 12 - 14% grade with a camping load. (My Raven now has two gears lower than that, and I am much happier on the steep grades.)
Your Sherpa has 26" wheels, with probably fatter tires--maybe 26 x 1.6" Supremes? I'd guess that with the 26" wheels, you could run an 11 - 34 cassette at the rear, and a 24-36-48 triple, and still have a low gear which is a bit lower than the 18.5 on my Eclipse. If I had such a Sherpa, though, I'd probably put a 22T small ring onto the front triple. I'd keep the 36T middle ring, however. I found that ring to be very useful on my Eclipse -- I did about 80% of my loaded riding on that ring.
Some people would find those ratios too low, others just right. You could get 2 or 3 different small chainrings for the front, say a 22T and a 24T (plus perhaps the more common 26T) and see which ones you like best, according to the terrain and the gear you're carrying.
Good luck in any case, and enjoy! We'll look forward to your stories & fotos.
Cheers,
John
