The way I have seen lenses made, that front element is the first part assembled. It looks like you have a teardown of that lens from your second picture, which you would likely need to reverse to get it apart, and will have to disassemble the entire lens to reach it.
If you open up the lens, you will be introducing even more dust as they are made in clean rooms.
Be aware, that after assembly, lenses need to be calibrated, which often requires specialized equipment to get it to have the autofocus work correctly.
I ignore the dust in my lenses as it doesn’t impact the ability to take pictures, and only when I stop down to f/22 do I even see it on one lens, and then only when on a solid colour, and only can see it when looking for it. All my other lenses, there is no dust spots I see in any photos, when my sensor is clean. If you have lots of dust spots in your photo, it may actually be dust on your sensor that is the cause.
With a lens that has an extension when zooming, there is no way to have it completely sealed, and will have some dust in it from it having to pull air in when extending.
Where did you get that diagram from? Did you find the repair manual for this lens? If so, can you please share a link?
- de Chuck King