Your question seems to be will grad school classes now help if you're entering medical school during 2003.
First of all, good grades in science courses will help you no matter what. That's the obvious answer.
Grad school classes is pretty broad. Without knowing what you're major is, or what your background is, so it's hard to answer without more specific information.
Any science classes you take will help you in medical school. Even if you get an F in anatomy now, it will help you to have seen some of the material when you take it in medical school, because the pace will be so fast. Immunology, Biochemistry, Anatomy, Microbiology, Cell and Molecular Biology, Physiology will all help.
Your question asks about helping you get admitted. If you are taking non-science graduate school courses, will it make sense to an admission's committee who is trying to judge how committed you are to medicine? If you are taking science graduate school courses that directly relate to something you will need in medicine, of course it will help you with admissions. It shows you are serious about medicine.
Perhaps your G.P.A. is low. If it is, then good grades in a science course will of course help show the admissions committees that you can do well in science courses, and may sway them if you are placed on a waitlist because of your grades.