'93 Audi 90S - oil leak
 

I've had some oil leaks for a while now but last week the one from the top of the engine (driver's side) got really bad. It leaks oil from the back of the engine, right on top of the sensor on the exhaust pipe. I assume it's the valve cover gasket. What do you think? How hard would you say the job is on a scale from 1 to 10?

Thanks :)