Gitane is a French company, and they have imported bicycles for many years. Most garden variety Gitanes come with the plastic Simplex derailleur system, and if it has a three piece cotterless crank, the bevel on the axle only works with three pin cranks, and replacement involves the whole thing.
If it is old enough to have French threading, that is a major problem. There used to be Frence, Italian and English threading, and English became the standard over time.
That's some of the main reasons knowing the age, and model would help. Do that and I can tell you all you need to know about it. As I said, I am a journeyman mechanic. I work part time at Burley Design Coop as a trailer assembler, wheel builder, or bicycle assembler currently several months a year.
I have the contacts to get info where my knowlege fails me. The people at Blue Heron, Revolution Cycles, Pauls Bicycle Way of Life, the Center for Appropriate Transportation or CAT as it is called here all reprocess and make big bucks off old machines.
CAT has a large loft full of them, and it has a charter school to teach youngsters how to build frames, and do other manufacture work on bicycles.
My good friend and former fellow Eugene Cycle Club racer Dan has Co-Motion Bicycles. Green Gear, the Bike Friday Company is here.
There is no doubt Eugene, Oregon is a city with many bicycle resources. I have worked in several shops here in Eugene and Portland over the years, Including Bike Gallery on Eastside in PDX. I have a Schwinn LeTourLuxe in excellent shape. It is a stable reliable touring bike, with cantilever brakes, and a frameset that handles the full load well. It is my token Schwinn and I ride it periodically in the Winter if I have to use panniers or a trailer.