Yeah, you need to get a Performa 200 if you want an Appletalk port. The Performa 200 is a Classic 2 with Appletalk and shittier components :P Alternatively, get a cool SE/30. All you need then is a farallon Ethernet transceiver. Works like an Appletalk to Ethernet conversor and as a mini hub too if you get the dual port model!
Anyway, to get the PCExchange program onto the Classic, this is what I did:
Loaded up Fusion. I had a System 7.5 hardfile lying around.
Inserted a disk, formatted it in Mac format.
Copied the PCExchange extension onto it.
Loaded the disk into the Classy.
Copied the Extension into the extensions folder
Mind you, I'm running 7.01, perhaps this 7.5 extension wont work on 6.x but I doubt it. Try it out!