Can dimensions be displayed?

 From:  Gerry (GERRYV)
My first post. I scanned the previous posts and didn't notice anything that asked this question so hopefully this isn't a repeat. I've no background in 3D although I've used Illustrator a lot. I'm looking for the easiest possible 3D learning curve but also, I hope to be able to show dimensions if possible as most of the things I expect to deal with will not freeform - mechanical device prototypes rather than jewelry for example.
Thanks much,
- Gerry