First make sure it is transmission fluid that you are dealing with. The rear main seal of the engine can leak into the bellhousing too.
The converter is probably fine as they are a sealed metal unit. There really isn't anything you can replace on it anyways. It could be the front shaft seal that you mentioned (quite likely) or possibly the front pump outer seal. After 30 years the front shaft seal is probably dried up and should be replaced. The pump outer seal is more involved but, unlike the front seal which has the rotating converter to seal with, the pump seal is a stationary devise so I wouldn't go there yet without first trying the shaft seal.