Leading Hand

I have a well travelled much loved C5 HDi estate, i drive around with the armrests down, unfortunately the drivers side has broken! Oh No! Its like i'm driving a different car, i have had a look and the plastic gubbins inside are busted, the question is, with a replacement, do you remove just the plastic malarkey, or does the metalwork have to come off? Not a major fault i know but it makes a big difference to me!