Did your GI give you the miralax/gatorade prep? It's not a bad prep at all, you just mix one bottle of miralax with 64 oz of gatorade. Some drs have you take 2-4 dulcolax first. The miralax has no taste so the only thing you taste is the gatorade. You might want to ask you dr about it if you have to do it again.
I hope everything goes well for you tomorrow,