Just take the servo off, give it a really good sand down and re-paint it! No need to buy a new one as they're quite expensive.
With the mk2, yours will be a 20mm servo. The Gti 16v model comes with the larger 22mm servo, it's an upgrade a lot of people make.
You can pick up a good condition 16v servo with master cylinder for £50 on forums and ebay.
Welcome to the world of mk2 ownership too!
