I did not use Medifast foods when I transitioned into maintenance nor do I use them now. In fact, I started the transition phase when I still had ~40#s more to lose and finished my weight loss eating healthy, whole foods. It took me a little longer (18 months) than if I had stayed with Medifast the entire time but that's what worked for me and my body.
I found 3FC to be a HUGE resource in checking out other healthy diet plans. I ended up using a combination of South Beach with some YOAD and ideas from the Vegetarian Lifestyle threads thrown in. South Beach gave me a good framework to know how much of each food group to have.
My personal choice is pretty much whole foods with no artificial sweeteners or ingredients or processed/packaged foods. Those diet plans helped me achieved that easily. If you find that you want to eat more commercial products, then South Beach would still be something worth looking into as well as Weight Watchers. Both will help guide you with healthy eating & maintenance.
It took me months to get maintenance right and it will always be something I must be vigilant about. I learned that I can NEVER go back to eating the portions and foods that I did when I was in my 20s. And yes, I do have goodies but they are occasional treats in proper amounts, not daily excursions into a calorie-laden abyss.
Right now I would suggest working the Medifast program as it is written. You will lose a lot of weight quickly. That gave me the motivation to continue on until I reached goal. Medifast will help you get used to smaller portion sizes and clean out your system of all the junky foods you ate before. Your palate will change & you will appreciate simple, whole foods. Then when you switch over to a more traditional diet or eating plan, you will already have some valuable tools & knowledge of proper eating behind you. Good luck!!