The biggest size you can print your graphic novel is 8x10", or you might want to use the square 8.25x8.25". (All the trim sizes are available here: https://www.createspace.com/Products/Book/#content3)
The white paper stock they use for colour books (60# smooth bright white off-set) is slightly different from the paper stock they use for B&W books (60# off-set). Both types are uncoated, CS do not offer a glossy stock. But the cover has a highly glossy laminate.
To calculate your costs, download this calculator: http://www.charltonbooks.com/CS-BookRoyaltyCalculator1.xls