If he's terminating each end too and has the equipment get him to test and certify each cable for you. Means you know they were working before he left. Proper labeling of each end is also essential.
Never run a single cable when it's just as easy to run 2 or more at the same time. Gives redundancy and/or expansion.
Technically possible with a layer 3 switch but routing is still required and best done with a purpose built router.