we don't have a kinko's here, but i just had a marquee printed at Staples, on glossy paper. it looks pretty good, although if it were a cpo, it would definately need to be covered with plexi. I dont reccomend going this route for marquees, since it looks very washed out with backlight, but with the light off it looks really good and would probably work very well for a cpo. best part was it was less than $5 to get printed (8.5" x 23") i dont know about Kinkos, but here at Staples, they can only print up to 24" wide in color, and 36" in black/white.
i dont know how big your panel is, mine is 12" x 30". i picked up a piece of plexi at Home Depot for like $9
you could probably save some money by going that route, but if you dont want plexi, i wouldnt reccomend the kinkos option.