Structural Engineer, Contractor, or Home Inspector- who to call?

I purchased a 40 year-old home four years ago and I've recently started some DIY projects. I pulled down some 70's style wood paneling and ceiling tiles and found hairline cracks in the ceiling (appears to be drywall) and a bigger crack in drywall. The stair moulding has separated from the wall. A web search mentions that these could be 'settlement cracks' but I want it checked out before I start any major renovation projects. Who is the best person to evaluate this- an engineer, a contractor or home inspector?