What to do if I suffer from high blood pressure and high cholesterol what would be a good and safe workout?

Walking, aerobics. First and foremost, of course, is to speak with your internist and to get your cholesterol and BP down. As for exercise, if your blood pressure is under control, you should be able to perform whatever activity you choose (though you should clear this with your internist first). If your BP remains high, though, i would suggest activities that do not stress the heart as much, i.e. Walking/aerobics.
Any form. Any form of regular exercise will help both. Walking is a good one. If you're runner, go for it. Swimming is good if it's warm enough where you are. Sports are the best because they're fun. I like to walk and listen to mp3s. If you enjoy your exercise, you're going to do it more and benefit more.