If you want a bike that'll last you, go for it. I have a Trek 760 from 84 that I'm working on and it is sweet.

It's not an '84 because I have the 84 catalog in my hand and the bike was red instead of blue and wasn't speced with campy. The 400 was the lowest end sport (as opposed to touring/road racing) bike for 84. I'm not sure what year yours is, but it should be a good ride on a well made frame.