Some things you may want to read to enhance your understanding, or perhaps employ as a reference in your essay. Or maybe just read for fun.
Antanas Maceina offers an interesting commentary on the metaphysical in The Grand Inquisitor here: http://www.lituanus.org/1969/69_2_03.htm
A straight-up summary for those who could use a refresher as you write the essay. Just don't confuse any of this as original analysis or insight. Since it's not, there's no reason to quote anything Ann Fremantle writes here: http://web.pdx.edu/~tothm/religion/Summary%20of%20The%20Grand%20Inquisitor.pdf
Might be a good idea to check out the Dostoevsky Research Station. Look at the Critical Essays section and other links posted below.
"The Legend of the Grand Inquisitor: The Utopian as Sadist" by Gordon Beauchamp, originally published in Humanitas
That's just a few to get you started. Don't forget to use the English Database page in our library system to check out many other pieces of scholarship on our readings, especially JSTOR, as we saw in class the other day.