Congratulations on your good fortune, Jason.
Two things. First, the burl will not tend to split the same way clear wood will. As Bill said, if the trunk grows straight through the middle, you can expect it to develop checks, but not the actual burl. If you cut with some branch/trunk to either side, it should store nicely. Past that, cut it any way you want to get the size and shape you plan to use. Just remember that the grain will tend to flow outward so quartersawn cuts will give you flames and cross cuts will give you swirls.
Second, remember that they'll continue to grow as long as they're on the tree. Think about whether you want to cut them now or later and, if later, consider them an investment that collects interest. Got one of those on my property as we speak. Currently the size of my head (actual head, not inflated ego one) and shooting for basketball +.
Good luck,
Dietrich