Homemade mayonnaise difficulties
You might want to try it by hand with a whisk first, rather than going straight to a blender, though a blender will work fine (though I've only done it with a standing blender, not an immersion blender)  The key I've found is the very slow addition of the oil to the beaten egg yolks.  (only yolks, no white).  You might want to taste your oil to make sure that it isn't rancid, which might be the cause of your "stinky" issue.  It does take some practice to pour the oil in slowly while you are beating the yolks, but you can add more oil at a time as your emulsion gets more stable.

I've found that it's not so hard to do by hand, and that you will get a real sense of accomplishment once you've done it.