Suggest taking a look at the spec lists of the Trek 520 and Bruce Gordon Rock n Roll for a jumpstart on touring specifics.

But, you are on the right track in thinking about a triple crank. The gearing on the triple is based on your own preference and the type of rear end the bike has. I (strongly) prefer half-step/granny gearing but this takes some study with a gear chart and a commitment to lots of double shifts that many dislike. A typical hs/g triple crank would be something like 46/42/24. The other option is so-called range gearing. A typical set up would be 48/34/24. Regardless of the gearing, a 110/74 triple is a safe bet with lots of options. Avoid road triples.

Regarding shifters, imo it depends on the gearing. For range gearing, I prefer barends as most of the shifts are single shifts on the rear. For hs/g gearing, I actually prefer DT shifters as it's possible to make 1-handed double shifts easily.

In terms of geometry, you can compare yours to many touring bikes here:
http://home.comcast.net/~pinnah/dirt...y-project.html

More thoughts on touring bikes here:
http://home.comcast.net/~pinnah/dirt...-function.html