What do you mean that your artwork "isn't being accepted to the program"? Are you trying open a 2d image in a 3d application? Or this program some place you're trying to apply to that doesn't like your 2d stuff?
If you have concept art and want to turn it into a 3d model, it doesn't matter which 3d application you use, so long as you pick one and stick with it. Blender and Maya are both good choices. Zbrush can be used in addition to these programs and is good for high poly sculpts and creating detailed bump maps and textures.
The benefit to learning Maya is that it's industry standard, can be used for a variety of applications in various fields, and it can handle importing/exporting any file type though you may need to install additional plugins.
The benefit for learning Blender is that it's free so you can make 3d commercial work right off the bat. Apparently it doesn't crash as often as Maya does.
If you have concept art in a character in tpose, you can use that file as a texture on a 2D plane. You can then model along the plane to get an accurate perimeter for your character. Here's good modeling tutorial: http://www.creativecrash.com/maya/tu...eling-tutorial