Congrats on your loss so far!
I can't speak specifically about the DVD you asked about (sorry) but I did start kettlebell exercise whilst very very unfit. It can be done and I noticed improvements in muscle tone fairly quickly, but the most important pieces of advice would hold true for any exercise: be careful of your technique to prevent injury and pace yourself to work within your current level of fitness and challenge it a bit. Like any weights-related exercise it can sometimes make your loss appear to stall temporarily (you can either put on muscle mass or retain some water as your muscles protect themselves from the activity), but the more muscle you have, the more calories your body is burning by just existing. As a man, you are blessed with the likelihood of putting on muscle mass more quickly than women!
Technique is important with kettlebells because extra weight is involved, so make sure you don't bend your knees too far (in a squat, for example, make sure your toes don't go forward past your knees) and protect your lower back - if it starts hurting immediately when you start an exercise then you probably should modify that exercise or swap it for another.
Pacing yourself is important with any exercise, because while you want to challenge your current level of fitness to improve it, you don't want to burn out in a flash. Because you're doing a DVD and not a class, you can pause when needed to get your breath back, shake out your muscles if they're really screaming, or grab some water. On the DVDs I do, some of the exercises were just too advanced when I started and so I modified them in a way that allowed me to finish, or did them more slowly/fewer reps. And most of them I can do now!
I actually started with Amy Bento's beginners kettlebell DVD (it's region 0, so although you order it from the US it works in UK players). This has a great introduction to technique, and the first workout is 20 minutes long and not as 'hardcore' as the kettleworx one I do now (I think kettlercise has even longer routines). This allowed me to make a start and build up to the harder routines whilst making sure I wouldn't hurt myself or overdo it. Even then, I still had to pause/pace when I first began!
Good luck, let us know what you decide to do.
Personally I love kettlebell training now!
