When using markers, specifically Sakura markers do I need to use some type of sealant on Yupo paper to protect my work?

Alcohol based markers like Sakura do not need any type of protective sealant since they dry quickly. Keep in mind that Yupo is a polypropylene sheet so no matter what medium you use, the pigment sits above the surface, never soaking into the paper like a traditional cotton or sulphite based paper.