What is the connection between this Parshah and the previous one?
Ramban (on 8:18): The Torah is presenting additional reasons 1 for ascribing Yisrael's victories over the Cana'anim to Hashem and not to their own prowess - because a. the Cana'anim are stronger than them and unconquerable, 2 b. their towns were fortified 'up to the heavens' and impregnable 3 and c. the family of the giants who lived there were invincible. 4
What are the implications of "Gedolim va'Atzumim mikem"?
Why does the Torah say "Shma Yisrael"?
Hadar Zekenim: A parable for this is a king who gave to his wife two pearls, and she lost one. He told her, guard the other one very well! So Yisrael said Na'aseh v'Nishma. When they made the Egel, it is as if they lost Na'aseh, for they transgressed Hashem's command "Lo Sa'aseh Lecha." The Torah reminds them "Shma"
Rashi (1:28, from Chulin 90b) writes that "uVetzuros ba'Shamayim" teaches that the Torah exaggerates. There it cites what the people heard from the spies. Is it not more reasonable that the Gemara learns from here, where the Torah itself says so?!
Refer to 1:28:1:1 and the note there.