Fan, USB-C board and removable disc drive have separate guides; Sony requires internet pairing when setting up a drive.
What to check before buying
Drive
iFixit documents replacing a faulty drive and installing a drive on a compatible digital Slim. Sony requires an internet connection for drive pairing at setup.
Cooling and ports
The fan and front USB-C board have different guides. Fan noise and an unresponsive front port are separate repair questions.