Not sure if it's as easy as it seems, but to get the whole marble chocolate and white cake do you simply just make one kind, pour it in the pan, then dollop the other kind and swirl it around?

you got it! Pour the white cake in the pan, then I try drizzle the chocolate evenly, then run a skewer or a knife through. Just remember to use only a portion of each mix so your pan doesn't overflow.
Good luck!

Actually, it doesn't give search results C.P.
You can use a marble cake mix or use a yellow cake mix and to 1 cup of the batter per each cake mix, mix in 1/4 cup cocoa powder.
Edited to add, then do as was already directed. Just wanted to add the options for making marble cakes from mixes. Some people advise alternating between the white and the chocolate to get a better pattern.
Hugs Squirrelly

OK i did A full search in the CAKE forums... Here is an old thread

http://www.cakecentral.com/cake-decorating-ftopict-4884-marble.html+cake

Hope this helps