...argues that there is no self because we are changing all the time
... I've read somewhere in the text that self is an illusion
(Just a warning, i'm not familiar with VCE philosophy or these *particular* authors)
These two things are one in the same, they are flip-sides of the same coin. I read through "The Bodhicaryavatara" (only half way) and on the surface, there is very little to do with the self (there is on a deeper, more obscure layer but not needed for you).
He seems to be an orthodox Mahayana Buddhist. Like all
orthodox Buddhists, he holds a similar position, the self is illusory and does not exist. It is hard to explain fully using English words but basically, everything in the universe is in a constant state of flux, this is
one reason why everything is impermanent and has no actual, permanent identity or self, including us. Another element, both found in Buddhist and western philosophy is this: everything which has parts depends on those parts for its existence and identity and therefore if theoretically imperfect and impermanent.
In Buddhist philosophy, it's important to note it doesn't deny an empirical (scientific) existence. I can see you and measure you, i know you exist in this moment. You also have continuity of existence, a name, an address, a VCAA number. However, in each moment you are different to the last. To explode this out, think of yourself 10 years ago and 10 years in the future, in both cases you
will be different from now, you might even almost seem like a different person over those time scales. That is sort of the idea that is trying to be captured.