Hi there
I dont use dvd's so cant comment on them, however if you are new to kettlebells take it slow. I recommend really learning the exercises esp compound ones such as snatch etc.., - Youtube will help, Steve Cotter shows some of the best way to hold the weight on youtube - and getting someone to check your form. Some of the exercises require specific movement/swinging a weight above your head stuff, and if done wrong even a 4.5kg weight can cause an injury. Is there a class near you that you can attend?
Having said that if weight loss is your goal kettlebells in a focsued session work a treat so good luck. You dont need to spend ages with them - 20-30mins a session x 3 times a week gets your body pumping the right sort of hormones and increasing your base metabolic rate to burn more fat.
Hope they work for you should be a great ivnestment