I'll keep this practical rather than theoretical as it should help you to understand this more through your own experience, and certainly more so than any amount of reading about it will.
From my point of view, to see no-self in things, is to see them as something that is not related to any self, as if it appears by itself.
If something can be observed, it cannot be that which observes it. If this is the case, see if you can catch what it is that is observing this experience as it unfolds.
And impermanence I see as how things come and go, seeing this with no attachment whatsoever.
What you're saying is correct, but it's much more subtle while at the same time being totally universal. Impermanence is there for all to see, but for it to make a change in the way you experience and understand the world you need to observe this in real-time. A theoretical understanding is one thing, the direct experience of it is quite another.
But to me it seems an insatisfaction with the perceived things is a sensation itself. Isn't it after all?
Perhaps I'm already perceiving suffering in the way is meant, but don't realize it.
It's a hugely complicated subject to be honest but I'll try to give you a simple example of suffering in action.
Remember a time when you really, really wanted something but couldn't have it? Or when you experienced something unpleasant which you wanted to avoid/get away from? Basically it comes down to craving and aversion. Craving is wanting something, aversion is not wanting something but they both operate on the same mechanism and lead to the same thing: Suffering/stress/dukkha.
Being dissatisfied with perceived things is a sensation, true, but so is stubbing your toe. You need to look at this more closely, look at how it is that no sensation can truly satisfy. Every sensation is impermanent and doesn't contain a self, how can anything that transient and empty ever lead to anything other than suffering? Why then do we cling to these things and hope that they'll make us happy? What will lead to a happiness independent of conditions?
Investigate your experience as it happens, see these things happen in real-time 'cause it makes it sooooooooo much clearer.