How to remove and replace window silicone between window and litchen wall?

I have had my kitchen partly wall tiled, there was woodchip on walls and up against UPVC windows, I have stripped the woodchip off and in doing so discovered that the window sealant was put on overlapping the woodchip, so, some sealant has come away and some woodhip still under sealant.
What is best way to re-seal, new sealant over old, or remove old, and how, should I re-plaster any gaps first also. ????............ Ta Dave