Hi John,
Tom gave you some good advise. Replacing the link coupler isn't all that hard to do. There's also a knuckle conversion that can replace a link coupler if that's you want. They work fine, but extend farther than the link ones, and make a larger gap between the cars. But if properly adjusted, the link couplers are just as reliable as any knuckle ones. If you need any more help with the trains, let us know. BTW, do you have any photos to share? Be careful though. My friend who is very into Lionel also acquired a few Flyer items, and he now has a LOT more!