Front control arms - Porsche 997.2

[Sisu9]

Just had the MOT and the mechanic said I could do with changing the 'tension rod' on the front right-hand side. I assume by this he means the wishbone lower control arm. I see in the US they are sometimes referred to as tension rods (I am in Finland so English was not the mechanic's first language).

2 questions:

Do I change both arms, even though only one is worn?
Should I also change coffin arms at the same time?

Did the outer tie rods about 5,000 kms back. Car is on 117,000kms.