Replace the old faucet valve

Hello everyone, in the photo you can see an old faucet in a WC flush tank. It can no longer be turned. Do I have to unscrew the valve at the marked spot with a pipe wrench and install a new one? Thanks Ashley

Honestly: New cistern, done. Everything else is botched, judging by the condition in the pictures. This has been in there for a few decades, hasn’t it!?