You'll be fine if you read nothing, but since this isn't really a plot driven show, I don't think you'll lose anything to read about it (even the wikipedia article on it is pretty good).
On the plus side, reading about it may help you stay on track in Act II (which can seem superfluous on first viewing which is a fault of the authors and not the audience) and by learning about both Seurat's development of chromoluminarism to blend colors and Sondheim's parallel staccato technique in the score may increase the depth of your appreciation for what you are seeing.
My guess is no matter what, when that final return to the beginning happens, you'll know you saw something remarkable. Have fun.
If the audience could do better, they'd be up here on stage and I'd be out there watching them. - Ethel Merman