I have an Alpha CB24 which is leaking?

can anyone help with my leaking boiler?

I have an Alpha CB24, which is currently leaking. The leak is not massive, a days leak can easily be cleaned up with a piece of kitchen roll, its more like a drip than a leak.

Is this a major problem for the boiler, is it easliy fixed by changing the washer or would it be more complex than that?

Thanks

Michelle