Mk2 diesel throttle valve leak

Hello everyone,

I have just bought myself Skoda Octavia mk2 FL 2010(59plate) vRS 2.0 Diesel on Manual. 
 

When i was inspecting car i noticed mild leak, but not sure of what it looked like oil but there is no oil attached to it, as far as i know coolant goes through it at the bottom. 
so my question is how much am i looking to change throttle valve or its piece of cake and i can do it myself?

p.s im not professional but i know what im doing hehe

Thanks and have a good weekend everyone