For qeustion 18, Alibre is definitely the more professional program for machine desigin, but if you want something easy to pick up and learn, try google sketchup. It's free, and helpful for other things as well (like remodelling!)
For question 12, check out meshcam and sheetcam as affordable 3D CAM programs -- they also have demos available for download.
For question 4, check out the gecko G540. It saves the cost of a breakout board, and is really an exceptional value.
Best regards,
Ahren
www.cncrouterparts.com