hi robyn, welcome aboard!
WELL DONE for giving up smoking. that is hands down the BEST thing you can do for your health. the links between smoking and cancer, lung disease, heart disease, vascular disease, strokes and other conditions are well established... you are at far greater risk being a skinny smoker than an overweight non-smoker!
good luck with losing the weight and becoming more active. walking is a great idea to get some exercise going
a few members of the forum are on meal replacements so you might be able to get advice from them
best of luck!