When I first went vegetarian, I actually gained weight, so you have to be careful. There's loads of vegetarian/vegan junkfood out there, so making that change doesn't necessarily mean you'll lose weight. It can also be overwhelming making a huge change like that all at once, on top of trying to lose weight. Definitely try adding in more fresh, whole foods, though.
Fruits, veggies, and whole grains are all great additions to any diet. If cholesterol is an issue, make sure you're getting enough fiber, it can help lower cholesterol levels. Cut down on saturated-fat levels as well (cut down on red meat or use leaner cuts, switch to skim milk or a non-dairy alternative, etc.) Also keep an eye on your sodium levels, that will help with blood pressure (you're supposed to get a max of 2300mg a day).
If you really want to go vegan, though, go for it! But I'd suggest making small changes over time, instead of all at once, so that it's not as overwhelming.

Good luck!