This is what i have been told so far. Every mechanic i have asked has said the same thing........the cogs would grind the plastic bit into millions of little pieces, then you can just flush it out.
One said that do not risk it. Im in two minds.
I think im going to go with the first one, if it does mess up, ill just replace it, would work out cheaper then getting the gearbox taken out then opened up and vice versa.
Good luck to me.