Derik,
Those questions really should have been asked before you had the site built.
It is a marketing tool and the scary thing is that many designers have never written an advert in their life.
As stated above, anyone CAN build a website.
Internet marketing however, is a lot more than that. As Warren said, there are two distinct phases, building and then promoting. What annoys me is that many so called designers do the first part and then leave the client high and dry by not doing the second.
Having a website and not promoting it is like having a fantastic leaflet but never delivering it.
In answer to your question about work, my cleaning sites do not get a huge amount of visitors but do convert pretty well. You certainly will not lose by having a decent site.