you can use black and white version in the alpha channel of a material to get land only (like it sounds like you want, and later a bump map in the bump or displacement channels to get relief. Don’t need an .ai file, it is usually done with a bitmap (save the illustrator as a psd file) just save with enough resolution in the bitmap that you get smooth enough results – there is no magic number, it just needs to be high enough resolution that it looks good as close as you are going to zoom in to the final object.