We've changed the fan , memory & hard drives in a couple of our laptops.. of course only after the warranty expires, but our used/refurbished ones only have 90 day warranty anyway..

Mainly takes very small screwdrivers, I think they do that on purpose, use very tiny screws...and they will strip out easy too...
most of the internal pieces just pop in/out..
each part has it own little cover on most of ours.. so less likey to put something in the wrong place..

and make sure no static or magnetic screwdrivers are around.. although I have used magnetic ones by accident and nothing happened.. but I don't go touching anything important like the motherboard or the soldered connections on it.