The switch itself is an easy swap. Use a new sealing washer to.
2 things to watch though.
First is that depending upon the age of your bike you might get an "upgraded" switch with a new type "weather pack" connector. This will need a bit of rewiring if it's the case in hand. Not hard though.
Secondly, and most importantly, don't overtighten it. You'll need a big spanner, 24mm I think, and it's easy to swing on it too hard. The thread is only 10mm and is in soft aluminium. It's easy to strip the thread. Hand tight and then a small "nip". Make sure it's not leaking and leave it.
You'll be fine...............

Forgot to mention, my bike had had it's 1 year/6k service 7 days before...!!!!!!

Strangely the dealer couldn't find the cause of the prob..!