bumperbob,
Generally speaking, repairs to this type of gauge must be done by a shop skilled in this task. There are some around and hopefully someone will pop in with a address or a web site.
The tube is filled with ether and is a sealed system. There is a Joe McGee method that has been outlined here to do this yourself, but I don't know how accurate or successful it turns out.
I will bet more info is on the way...maybe from the land of sandwiches!
Stuart
