What parts can I replace myself on the HP EliteBook 840 G5, and which require an authorized service provider?

Customer Self-Repair parts include the AC adapter, solid-state drive, memory module, WLAN module, WWAN module, and keyboard. Parts such as the battery, heat sink, system board, fan, display assembly, and speaker assembly should only be accessed by an authorized service provider, as accessing them can damage the computer or void the warranty. (Page 3, Page 6)