K-3's parallaxless reflex viewfinder dust problem

Hi everybody,
Nice to found here in this forum
I just reveived my K3 film camera. I haven't load film to test it yet.
But the inside glass of the reflex viewfinder is very dirty with dust. I remove the lens and in the upper place of the camera I found the reflex glass. I use a blower but I can't reach the place behind the glass. Do I have to open the camera to clean it? Any other solutions possible?

Thanks,
Cleon