Whatever you do, make sure that you do both aerobic AND anaerobic exercises. Running 3 miles, even at a quick pace is NOT enough if you want to make it. Make sure you work in some sprinting intervals or do maximum effort intervals on a bike at gym...or both. Seriously, you can run all of the long distance that you want, but that is only half of it. Wrestling is very much so an anaerobic sport...that's why the sprinting and maximum effort stuff will be vital to you not gassing/pooping out too soon. Make sure you mix it up in your routine; do both aerobic AND anaerobic. haha, I can't stress it enough.
I would also recommend to focus on body-weight exercises moreso than weights, but THAT, is merely a personal preference. To me, it is no surprise that the best fighter in MMA right now (Fedor) is not a weight lifter... but to each his own. I would recommend dips, pushups, hand-stand pushups against a wall, and last but not least, pullups. For legs, doing lunges (with or without weight) is great for wrestling, and also doing some explosive jump squats (without weight) would be a big helper. Also, just a thought, maybe start training grip, as grip strength is vital in any grappling.
Eating/dieting...well, that all depends...how much do you weigh now? If you are a heavy weight, your "diet" will probably be quite a bit different than that of a 155 pounder...hope this helped a lil'.
