CAD is a bottomless, time sucking, turning avoiding, pit!
An opinionated commentary on CAD for turners:
I have used Sketchup, and it is neat. I have used TurboCad and it is a bargain and rich in function. I have used CAD off and on over the years, including designing furniture and a cabin. I have a computer science background. I worked my way thru school as a draftsman. I now use a "T" square, ruler and board, and a copier to save and modify different versions of my drawing.
Unless you want to spend nearly as much time learning and maintaining your CAD skills as you do turning follow the advice in the message above to use grid pages and cutouts and a 1/4" = 1' architectural scale (ruler.)
Don't get me wrong. CAD is great. CAD is fun. CAD is a great consumer of time. CAD can be a game. But your head and your neck will ache. Just be sure you want to give up a large part of your turning time to even begin to get results you want.
Also consider making everything in your shop wheeled or semi movable. In spite of my obsessive planning (which was worth it) I continue to reconfigure my shop semi-permanently or temporarily (say for turning meetings.)
It's a choice. I made mine. Pencil, 1/4" grid paper, scale, scissors, and a copier, and wheels on everything that touches the floor, and hangers (french cleats) for everything on the walls.
Jerry