Hi @gsuzam,
Many thanks for your question and welcome to the Bunnings Workshop community, it is fantastic to have you join us.
What you've described is exactly what you'll need to do.
Remove the silicone using a utility knife to cut it away from the shower frame. Ensure you wear gloves and long protective clothing to reduce the risk of lacerations.
Once the silicone is removed, give the area a good clean with hot soapy water to remove any dirt or grime that has built up. Once clean, allow the area to thoroughly dry.
Once everything is dry, you'll need a caulking gun and some Sika Translucent Kitchen And Bathroom Silicone Sealant to seal the gaps. Pay close attention to the grout lines because they are the low spots where it's likely water can get out. Apply enough silicone to cover the gap and strike it off using a Silicone Scraper to get a nice clean bead.
Caulking is a skill that if you're a beginner can be very messy. This is all part of learning, but it's good to be prepared for the clean-up. Keep a bucket of water close by and plenty of rags to clean up.
You might like to check out How To Silicone a Gap for some additional guidance.
Let me know if you have any further questions.
Jacob
