Looks to me you are just starting to learn, that's OK.
But if you like to start with a project that does 3 modes of communication (CAN, GSM, Ethernet) as well as GPS, that seems a bit ambitious to me.
However, if you are researching the possibilities of an Arduino doing this, research the following:
Do your selected devices use any Arduino pins for different purposes, and without a possibility to change these pins.
And the possibility to change pins doesn't only mean by hardware, but also by the functions those Arduino pins offer.
I'm pretty sure all shields can be stacked.
But will they still work together while stacked, no idea.
If there's no conclusive answer (maybe because no one reading here has ever tried this combination), you'll have to do this research yourself.
If you find a problem you can always ask a specific question about that.