The fact that the seat-lug isn't a split-type clamp should mean the lug is repairable e.g. use a metal-filled epoxy. Depends on how big / where the crack goes?
You should be able to source a suitable toptube rubber cable grommet from somewhere.
In terms of restoration, it depends on whether you're DIYing and what degree of finish you want e.g new transfers etc?
If it was mine, I'd do a lot of the rubbing down / prep myself, repaint the lugs, apply transfers and get an automotive finisher to apply a suitable low-bake clearcoat lacquer.