Ok...I'll try this. 1. No, I would not "finish" or treat the inside of the cabinet with anything, leave it raw. 2. Check online for places that sell SC, I've even seen it being sold on ebay. I got luck and found some beautiful 3/8" T&G at a local supply house. 3. I've never heard of plywood spanish cedar, if it's available I don't see why it wouldn't work. I believe Slim had a site for Spanish Cedar....I'll see if I can dig it up, but I am sure Google will find you something.