Hi @amarnaik,
Welcome to the Bunnings Workshop community, it is fantastic to have you with us.
Your thoughts that you would need to remove the current sealer and replace it would be correct.
To remove the sealer, you will have to grind it back. This can be done with specially designed Concrete Grinders, which incorporate dust control ports that can be connected to a dust extractor. You could also use an angle grinder with a concrete grinding disc, but they do not have dust control measures and would not be as good for this work.
Regardless of dust control measures, either of these options will create airborne concrete dust, which is harmful if inhaled, so you will have to wear a P2 mask or, better, a P2 Half Face Respirator alongside eye protection, hearing protection, long protective clothing, gloves and enclosed shoes.
Once the sealer has been removed, you can apply a new sealer such as Crommelin Gloss Wet Look Concrete And Paving Sealer or Crommelin Clear Satin DiamondTough Concrete & Paving Sealer, depending on the look you are after. Ensure you follow the application steps on your product of choice closely as this will ensure you get the best results possible.
Let me know what you think, and if you have further questions, please don't hesitate to ask.
Jacob
