You can do it, but it will be a big transition for you. It might make sense to start by becoming vegetarian for a month, then transitioning to vegan, and then moving on to raw. If your goal is to stay with it longer term, this might be more effective.
Any drastic, sudden change in your diet can shock your system and have negative health effects especially if you're cutting out something your body is used to. Simply doing it is not likely to cause any major health issues (although check with your doctor on this), but adjusting to the lifestyle and doing it healthfully is another story.
Vegan, as I'm sure you are aware, means absolutely no animal products whatsoever. This includes the obvious meats, poultry, and fish, but anything that comes from an animal also like cheese, milk, eggs, chicken soup, things cooked in chicken or beef stock or flavored with it, etc. It's certainly a lifestyle choice that is not for everyone.
Be aware that there's a lot vital nutrients that we take in from animal products that you will need to find in other places. Iron, Calcium, Protein, B12, and some others are necessary to be healthy. You will need to find alternative ways to get these nutrients or you run the risk of getting malnourished and very, very sick. Prolonged malnourishment or deficencies in certain things can lead to other health problems.
On the other hand if you "go vegan" for any significant amount of time and then suddenly eat some sort of meat accidentally or on purpose your body can be shocked by it (not being used to it) and you may feel sick.
Veganism is more a choice of lifestyle than a diet though. Yes it's low in fat and cholesterol but it's very high in carbohydrates and (potentially) high in salt, depending on what you eat. Depending on how/where you live you also might find it extremely difficult to live on raw fruits and vegetables exclusively. And again, you won't be getting a lot of the nutrients you need for a healthy diet. You'll probably lose SOME weight, but just eating fruits and vegetables won't be the total answer. A lot of these people are healthy individuals BUT...overweight and fat Vegetarians and Vegans DO exist.
I did a (mostly) veggie diet a few years ago (although I still ate some fish and chicken on occasion) and it didn't work out for me. I lost a few pounds, not really enough to be noticeable even and my energy crashed, I was always starving, tired, and generally miserable.
My point is that going vegan is a lifestyle choice which is based more on personal beliefs and convictions than losing weight and being healthy. You might not get the results you want and if you don't do it properly you can harm yourself. You REALLY should talk it over with your doctor before going into it as he/she can tell you more about what you need to do to make sure you're taking in all the vitamins, minerals, and nutrients you need.