Yes, you can upgrade the internal card. Just pop off the back cover and swap it out.
There is a photo of the internal microSD location here:
https://www.mobileread.com/forums/sho...=111673&page=2
I know that an 8GB microSD will work. don't know about the class of the included internal 2 GB card.
Regarding cases/protectors, see this thread:
https://www.mobileread.com/forums/sho...d.php?t=111548
No idea about the screen protector.
Cheers