Minor renovation and alterations, what should I expect?

I am looking to do a couple minor renovations and alterations in a browstone. I’d like some advice on whether I need to hire a general contractor for this job or if I should be hiring directly. In all cases, what should I expect to pay, roughly? I am looking to do the following:

* Refinish the hardwood floors and staircase
* Repaint a few rooms
* Install conduit through the walls for networking etc
* Install an exhaust hood in the kitchen

The last point strikes me as potentially the heaviest as it involves passing a duct through the cabinets and through the back brick wall. If I do need a contractor, I would love some recommendations (this house is in Bed Stuy)