ok, now that you know what you've got and what you wanna do with the gearing......how much of what came with the bike can you keep?

what is the condition of the chainrings and cogs? sharkfins?
how about the chain? worn out and/or stretched?
are the crankarms the proper length for your legs?

the rear cassette, if not worn, should be a keeper.
you can change individual chainrings, but might find it cheaper to just buy a new crankset on ebay.
you don't wanna switch only the inner ring........derailler may not take up the slack, too big of a jump between rings, and the big ring will be useless for a "mature" gentleman touring with gear.
plan on replacing the chain.