my $.02 is to go for the basic conversion for the bars, add new 1.5"-1.75" street tires and don't touch the drive train or wheels unless it doesn't work. For lightly loaded touring the regular Schwalbes are kinda heavy and slow, for your money you can find nicer basic tires, sure if money is no object spend $150 on a pair of Marathon Supremes but you could do just as well with some Panaracers for almost half the price.
The reason for not going whole hog on the conversion for new parts, especially high end parts on everything is your statement that you're new to touring and are thinking of getting a LHT down the line. Your ability to go from point A to point B with a brand new $300 drive train or the old one will be no different and you may discover you like the bike and don't want to cannibalize it for a new frame.