Brian - sorry it took me a while to catch up with your Stepwagon Trials! You seem to have a Friday vehicle as the problems seem to be arriving like buses!
I guess the risk of a grey import is exactly what you are experiencing - there are no detailed service manuals in English for these as you have found out so the best approach might be using a car electrics specialist - does your stepwagon have a plug in diagnosis connection? I would expect one and it is likely to have standard OBD II codes to show what is wrong. (see here: http://www.obd-codes.com/trouble_codes/honda/) However diagnosis and cure are different animals!
As I guess you know, finding electrical faults takes time and can therefore be costly. A lot comes back to the car mechanic and the best ones are probably not at the Honda dealer but some back street car specialist. Can't advise where to find one in your area though.
I hope you turn the corner soon and get back to enjoying Japan's secret mid sized van!
Lewis