1. Socks. I tend to buy new balance cotton socks, if sweating is a problem in cotton you can get socks that are made with moisture wicking fabric (aka coolmax, dri fit, etc.) They aren't cheap but if you sweat in cotton thats the only way to go. I but a lot of (generally not sock related) stuff from tenniswarehouse.com and they have really good service and really good prices on clothing and I know they sell lots of socks.
Shoes, new balance. Go to a New Balance store if you can. They have industry best customer service. They will measure the length and width of both of your feet and recommend shoe styles that are good for you foot shape (ie pronated, supinated, flat arch, high arch etc). Just walk in, tell them you want non leather walking shoes, they will narrow it down to a couple of choices for you and get you the perfect size. Expect to pay $80 and up but I walk a lot and generally get 18 months out of a pair of New Balance.