Some parts for the Express can still be purchased from motorcycle shops. I have been able to get most of what I need from Everett Powersports (formally Everett Honda Shop) in Everett Washington.
If you arnt near any place like that you might ask around here.
As for giving it a tuneup, I have had many people come to me saying they took their Express in for a tuneup and it still doesnt run. Turns out the places did little more then clean the bowl of the carb out and charge them a fortune.
If you think you have the know-how to do it yourself, my Express guide can probably tell you what you need.
The guide was ment for bikes that have sat a year or more.