If you don't understand how the parts work, what they do, how delicate the connectors are... Without any experience you can't know what not to do. Trying to build a PC, a lot can go wrong if you don't know what you're doing. That a lot of expensive parts that can be destroyed in a blink of an eye if you make a mistake.
You say all the parts fit only one way. Well, that depends on how clumsy or ignorant the builder is. Or both