shocking the body with different cardio is bull****. yes, as snitch said, there's specificity of training. and there's diminishing rates of return. and there's the general principle that if your goal is to be a generally well-rounded athlete, it makes sense to do different sports. but that's different from "shocking the body".
anyway, if you want to start running: be VERY aware of doing too much too soon. it's very easy to get injured (and i say this as a runner myself). if you want to do it anyway, DON'T start with a race. start with
http://www.c25k.com/ and follow the program (if it's feels way too easy, you can skip the first few weeks). your body needs a long time to adapt to the demands of running. your muscles adapt quite fast (at least the major ones), your bones and ligaments extremely slowly (we're talking years here). so again: take it VERY easy.
but i think there are better alternatives available to you ATM. you can switch the ellipticals for rowing, stairmaster, stepper, cycling etc... or you can stay on the elliptical but do a more interesting workout then "60 minutes at 15 resistance": warm up, then do "1 min hard", "2min easy" & repeat then do a cool down. or do a form of pyramid intervals. etc