Lia - Most of us are in other challenges as well so I don't think anyone will have a problem with it!
As far as her DVD's go, I started with her original Walk Away the Pounds Deluxe set (1,2 and 3 miles). You may want to start with a 3 or 4 mile since you're already exercising. I wasn't. The Walk Slim series are pretty good workouts that don't need any other equipment. Some of her DVD's require weights and/or resistance bands/stretch bands. A good way to get a better idea which one may work for you is to read the reviews on Amazon.com. My favorites right now are Walk Slim - 4 Fast Miles and Walk & Kick. Hope that helps.