You can go here:
http://www.airgunhome.com/agforum/viewtopic.php?t=37
I've put up the Crosman owners manual that applies to that time period and used the 10-oz CO2 refill tank.
The tank may not be refillable anywhere- depends on what fitting is on it and if they check to see if it's currently certified (all tanks that hold pressurized substances have a "lifespan" and have to be re-certified or disposed of periodically- like a propane barbecue tank which is only certified for 10 years. That being said, you could buy a 9 or 12-0z paintball tank and get the correct fitting put on it to use the gun if you so desired- or get the right fitting, attach it to a paintball gun hose and run to the tank so the gas is always connected and available to the gun.
Is it too much of an "antique" to use? Seals probably all shot to heck- so they'd need to be replaced before anything, and beyond that- unless you're a collector, or someone is willing to pay you good money for it- why not shoot it?