I would like to renew the silver cover with the numbers on that is on the gearstick as its looking a bit worn how do I remove it.

Get a small flat screw driver and prise it out.

I recently changed the silver insert on my Fabia as it was shabby and it just levered out. I assume the Octavia is the same, although I'm not sure as my Octavia is a DSG and has a totally different shifter to the manual.

Yep little screw driver/trim tool and it will pop out. Push the new one in and bobs your uncle

Probably the best £6 I spent on my car, replacing that bit of the gear knob. Made a big difference to the look & feel of the cabin, probably as the gear lever is such a prominent thing in the middle, and something you touch potentially hundreds of times a journey.