My Golf is leaking transmission oil slowly. I have located it to the push rod that enters the gearbox to select the gear. I'm assuming the rubber seal needs replacing.

Has anyone replaced this before and knows how tricky it is?

I'm assuming I can dig out the old one and push a new seal in its place. But the next problem is where to find the seal. I guess a VW main dealer should supply them; my local parts shop didn't have it.