Congratulations on beating withdrawal and finding yoga. I have books and guided meditations from Kripalu and they are one of the good traditions to check out.
Newbies to yoga should be aware that there are many lineages and a lot of non-lineage instructors. You might find a well trained yoga teacher at a health club or you might get an aerobics instructor who knows enough to fill in the yoga slot at the franchise. A good class should welcome beginners and give them a little extra attention. It should include some grounding techniques at the beginning to shift focus from your busy day to the present moment. Not all classes can include full meditation periods at the end because of time constraints but if you don't finish with some version of "corpse pose" then you are being cheated out of the core of yoga practice. The reason you tame the body with all that stretching is so that it is quiet while you begin the inner work of learning about your own mind.
Please forgive my lecture, I'm not a yoga teacher. But I am a yoga nerd who has been practicing and researching for over 15 years.
Also I have to say that yoga is for all body types. I am obese, not svelte, and compact not willowy but I learned that the correct form of every posture is dependent on the breath not the vehicle.
Thanks for sharing your journey.