My own experiance as hobbiest, then repair technician, and now student in official IT in training. The better part of a weekend is only true with some serious setbacks. Likewise a half hour for assembly is only true if you’re familiar with the specific parts. For example the new connectors for heatsinks take a little figuring out if you haven’t installed one before. Computer cases can have little problems to figure out.
I’d have to say hardware assembly is about an hour on average. Half hour if it goes perfect, longer if it don’t. Software installation and configuration, including operating system, drivers, security/male-ware protection, utilities, and applications. Maybe about 4 hours. That one is highly variable.