I haven't done it on my RRS but I replaced the plastic paddles on my Jag XKR with OEM silver metal ones (If I recall right, LR had both silver and red ones as upgrades, but for whatever reason Jag only offered the red ones as a Jag part, but they are otherwise identical to the LR parts and I preferred the silver to the red).
It was a 5 minute job, dead easy. I seemed to remember it required a #9 or maybe a #10 torx (just one torx screw per paddle).
The OEM paddles are very overpriced though, for what really is just a couple of simple metal levers over cheap micoswitches.
Feeling metal shifters under your hands is much nicer though. It made the Jag feel even more reminiscent of Astons I've driven, which is what I was going for. The OEM metal paddles have a shorter motion but a more affirmative click than the plastic ones.
Given how much such a small thing improves the driving feel, it boggles my mind why Jag/LR ever went with plastic shifters.