A few thoughts.

First yes, it's definitely possible to lose weight and get fitter just by walking more. If you walk briskly enough it's cardio.

Second, you say you want to tone up. I really recommend either pilates or yoga for that. Those won't help you lose weight but they'll tone your muscles and build your strength which will help general fitness. You can get some great videos on YouTube- I recommend Adrienne yoga.

Lastly your shoes - runners do gait analysis and I don't see why you can't have that done for walking too- most sports shops offer it. They film you on a treadmill and slow the footage down and from that advise what shoes are best. Some people benefit from orthotics for support.