First off, congrats for starting your first WOD! I just started them last month, even though I'd seen them for 3+ months prior ... they are intimidating for sure, but in time, doable.
I'm 37 years old, 10-lbs overweight, and in moderately good physical condition. These workouts have taken me to another level in only a month, and I look back at my "old" workout routines and think, 'how boring!' ... I'm aiming to be a hellishly fit 40-year old so I can keep up with my two toddlers as well as try some serious parkour moves.
One thing that helped me prepare for the WOD - and this was completely by accident - was the Mens Health Bellyoff! Bodyweight II program; I used to be 40-lbs overweight. Here's a link to the program:
http://www.menshealth.com/bellyoff/Also look into workouts called "grease the groove" ... I learned about them on this forum, and they work really well.
Good luck, and keep at it!