I'm in a similar situation currently and already in paramedic school. I'm one of about 15 paramedics/students I can think of that are extremely over weight. In the last month I've bought a bike and started watching a little more closely what I eat and cutting out fast food (I've slipped up lately and I felt terrible about it). I still drink sodas but not like before, before I could almost finish off a 12 pack in a day. My crutch right now though is sweet tea, I generally drink water, sweet tea, or crystal light. I limit myself to one soda if I have to have one, and it's usually something like a Coke Zero or Pepsi Zero, to get the soda feel but not as much bad crap.
When we shop we don't buy beef, anything we use alot that has high fructose corn syrup in it. We buy mainly ground pork and turkey, chicken breasts, salmon, white fish (cod or whatever we can get cheaply). Multigrain breads for our breads, and I allow my self a breakfeast treat of an 'Everything Bagel' from Panera Breads (my wife is a baker there).
My issue has been my eating habits lately. I don't over eat at the meals but I will eat maybe once or twice a day sometimes over a 15-18 hour period.
I ride when possible, at the very least 2 or 3 times a week and a min of 3 miles (very hilly terrain around here). My crutches to take care of still; eating out, soda, my eating habits (times).
count your calories. eat veggies, (lots) and avoid any/all breaded meats and deep fried foods. and stay away from all things white. (white bread, white rice, etc.) and limit yourself to 2,200 cals per day. Ditch the soda ("diet" is "ok" but eventually it's gotta be kicked to the curb 100%) and find a good workout routine for you.
hundredpushups.com + twohundredsitups.com + twohundredsquats.com are good programs. do each one the same day, PU, SU, and squats.
on top with the above mentioned info, You'll drop body fat, and gain muscle mass. (you already have enough body fat to fuel the muscle growth, don't worry about that, and no, I'm not making fun of you in any way, shape, nor form. I'm speaking from experience) and all you're blood work will be astounding. (mine is)
And when your wife starts checking your new pecks, built shoulders, and semi-ripped chest... Oh yeah bro!
If the above aren't that appealing to you, firegrounds.com is an excellent workout routine. do their 28 Day program, to "get into shape" repeat as many times as you need (the 28 days) and than get into L1, L2, etc. etc. as your body becomes more and more ready. Many ways exist that you can go about doing this.
But above all, NEVER QUIT! B)