G'day
Do NOT fill with sillicone or anything else, the guy doing the work will happily put the bill up
If the gelcoat is scratched and not chipped (can you see fibreglass matting underneath?) Then it's ok to use.
The danger with exposed fibreglass matting where the resin has been chipped away is that over time water can and will get in, causing osmosis. this is the equivalent of rust or cancer.
Te repair it's an easy cosmetic job, get someone who knows what they're doing. Only use gelcoat or flowcoat depending on method of repair, nothing foreign like miracle putties or silicones etc.
Dave