I think it would be a drastic measure, to go on an all out diet just for 10 lbs.
It's enough that you've noticed a difference in the mirror in my opinion. It's a good sign that you want to change your diet to a healthier one (as opposed to the junk food that you're eating at the moment).
There are loads of places on the web that you can get diet information from if you did want more information on a balanced diet.
A moderate healthy diet isn't rocket science though. You should be drinking plenty of water, eating 6 small, regular meals a day and you should try and get enough fruit and veg.
Try not to eat red meat more than once or twice a week, and make sure that you have enough nutrients and etc. in your diet.
It's best to get it fresh into your diet.
I know that on http://www.realage.com they do a questionnaire that asks a variety of questions relating to your lifestyle and your diet. It gives you a 'real age', and then it gives you a print off that you can work on.
However, I think that it would be irresponsible of me just to say that it's down to diet. You would dramatically increase your quality of life, and your health, if you made time out of your busy work schedule to exercise, as well as eat properly.
It's like climbing a mountain on half fuel. I know that work is work, and it's hard, but if you're not taking good care of yourself, you're climbing that mountain on poor fuel, and not enough of it.
Keep snacks with you to help you throughout the day so you won't reach for potato chips or a chocolate bar - which will end up making you feel worse off than when you began.