Probably not cable stretch. Not sure which campy group it has but you need to fix/replace the shifters first thing. You need pedals or the correct cleats. I don't see any reason the change the fork and handlebars unless they are damaged. The 3.0 is a good frame if only a little stiff - the parts mix is a jumble of this-n-that but as long as it runs who cares. (I do have the same Time cleats that you are welcome to if you decide to use the Time pedals - just let me know).
Gary