hot test before you leave
The hardware seller I go to will hot test the motherboard with the cpu and memory installed right there before you leave. That guarantees the state of the hardware before you leave so there is no argument about it if something turns up bad later and it saves you a round trip to replace an item. The young guys that work there are highly knowledgeable and will suggest variations for you if asked and will warn you if some of your choices have negative side effects with your package.