Its hard drive, optical drive and fan system have distinct guides; a disc-read fault is not the same repair as a full drive.
What to check before buying
Disc mechanism
iFixit documents an optical-drive swap and notes that cables may need to transfer from the old unit. A console that cannot read discs differs from one with a failing game-storage drive.
Storage and cooling
The hard drive and fan have their own procedures. The Slim's chassis and parts differ from the larger original and Pro PS4.