APU probably needs reflowing.
No, just the laser is fine. Do not replace the optical drive PCB or your system will not be able to read discs.
I hope you kept the original PCB because if not, sorry to say but you'll never be able to use physical games again…. The Renesas chip is on that PCB and it’s married to your console’s APU.
The system will always throw error CE-34335-8 if there’s no HDD inserted, it cannot boot without it. Your other error code indicates the new HDD is faulty.