Yeah, I think maybe $150 is a decent price since the fridge is complete and will clean up well, but you'll have to chance it with the gasket on the freezer door. If it's no longer sealing effectively, you may be defrosting the freezer every few months at least, even if you don't access it much. Modern may still have the correct Gemline replacement gasket, but it won't be cheap. That's where I got gaskets for my '57 and I've been amazed by how little frost forms in the freezer now.
What's up with the wide range in shipping rates that they quoted you? You might want to enter "shipping" into the Searchalator and check old threads. There's a truck driver whose name I can never remember but she's cheap and good, and has hauled machines for a number of members here.
This fridge seems fairly uncommon and sort of like a transitional model. If it won't break the bank, I think it's worth pursuing.