I personally don't like mounting the motherboard in a case.
But that has become much easier over time.

Processors are very easy too now, compared to a dozen years ago.

Aside from those two, everything else is quite easy to do.
The motherboard manual explains a lot.
And most of the plugs will only go one way.

Lots of resources on building systems too.

Still, the last system I bought, was pre made.
It cost $200 or so more then the parts.
But comes with what they call an IPR.
If at any point in 4 years from the purchase date, anything burns out or expires, they replace the part with a brand new (not refurbished) same piece free. If they no longer carry that piece, then its whatever the modern version is.

I like that warranty, and still remember cracking a motherboard many years ago.