Known as "Da Book" among fountain pen collectors, Fountain Pens: The Complete Guide to Repair & Restoration a self-published volume by Frank Dubiel.

Mr. Dubiel's book documents how to effect repairs on vintage fountain pens. His assumption is that most of the pens in the scope of his book have not been produced in, at best, a quarter-century. Even in their heyday, repairs were often accomplished by "remove defective widget with widget removal pliers ($1.00 net.) and replace with new widget ($.05 net.)" (direct quote from Da Book). Given that the replacement "widgets" may be scarce at best, making do with what you have is given a high value. This may require some improvisation or even cannibalization. Repairs documented range from simply replacing an ink sack, to manufacturing a replacement part on advanced tools.

It is generally held that anyone attempting repairs of vintage fountain pens must own a copy of Da Book. Truthfully, anyone interested in collecting vintage fountain pens should own a copy, even if the most simple of repairs will not be attempted. It gives an excellent overview of how things within a fountain pen may work, even on older techniques and technologies. Further, it provides an interesting historical perspective. Finally, if looking to buy a pen at a flea market, it will help make an informed decision as to the condition of the pen, and the effort to repair.

Mr. Dubiel passed away on December 7, 2003. The pen community will truely miss him.

Sources:
Fountain Pens: The Complete Guide to Repair & Restoration
The Zoss Pen List