um, unles you knows what you're doing, and/or prepared to spend a load of time learning a skill you won't use much (hopefully!) i wd get a bloke who does gelcoat repairs - not v expensive to have the scuffs taken out so it looks new. The marina staff wil definitely knopw the right people to talk to.
You can do the work yourself, but if you're not happy having the scuff, you probably won't be happy with a less-than-decent repair. So, the other option is to lower your standards, park the boat such that you can't see the scuffs, and spend a fraction of the repair money on strong drinks.
I had a little scuff near the bow year before last. I looked up how to do the repair on the internet, bought polishes and gel coat which all seem to sell for about £10 each together with cling film, different sandpapers, hair dryer etc etc. At the end of the season the scuff was properly repaired as part of the winter service for EUR30!
Agree with tcm on this. It is pointless trying to do this yourself, far easier to let someone with all the right kit AND the expertise to do it for you. You will be a lot happier with the final outcome.