I bought some plants from Willis a few years ago. They were guaranteed. None of them survived because they had hardly any roots. To use the guarantee, they require you to send the bottom half of the plant back. I did and got replacements. None of them survived. 2 years of my life gone. So I bought new plants elsewhere. Check around and you'll find others with similar experiences. Isons has a good reputation and their founder developed the Ison variety, one of the best all around varieties for fresh eating, jelly, and winemaking. It's also a good pollinator.
edited to add: You should try to get virus free cloned vines, but your wild ones will probably bring every known virus and disease that muscadines are susceptible to into your vineyard. Fortunately, they can live with and survive almost anything. Speaking of dangers to muscadines, if there are row crop operations around you or anybody using 2,4-D or dicamba herbicides, they drift and the slightest whiff of them will damage any grape including muscadines.