I have never used Medifast personally, but a quick glance at their nutrition facts, and I would say if you are struggling with high cholesterol, I wouldn't go that route. Any pre-packaged items/shakes like that tend to be high in sodium and cholesterol- two things you want to stay away from.
As with any diet- I'd ask your doctor before you start any plan to make sure it's right for you. I know losing weight can be tough! My husband went on a strict diet of mostly greens and other vegetables and that's what helped him a lot.
Good luck!