Very, but it depends on the nature of the apocalypse. In a sense, your physical infrastructure is there. You have materials available with very little need to refine. You have shelter. If you have fewer survivors, you have lesser needs - fire for warmth, water can be filtered or boiled to a lesser extent than modern municipal water. Rather than large scale, you'd work on a smaller scale - engines running as generators off scounged power or water gas for example.

Useful skills would vary. A smart engineer would be as valuable as your average paranoid survivalist or your rien faire enthusiast. Copper cable is useful for power or 'low tech' tools. Cars could be useful modified as horse carts, running off water gas or simply water resistant storage. 

If I *was* in an apocalypse, I'd consider cities to be an easier place to survive, both in terms of resources and *defensibly* for a city slicker than the countryside, or the wilderness. 

One could salvage household piping, and other materials, reuse existing shelters with repairs and so on much more easily than remaking it.