92 Acura Legend still runs hot after engine changed

What is your question?

My sister had engine replaced for damage due to fluctuating overheating til engine ruined. First day of driving, car overheats. Mechanic said engine pressures were fine; says problem is a hose on top of the engine. Can the issue now be the heater core? Where is the core located and does the whole dash have to come out? What are the steps? Tools? Precautions.