No dumb questions here 4runner
The size of the stem is a good indicator. I normally try to stick with stems as thick as a pencil or larger. However, you can gently loosen the soil and brush back the dirt enough to see the neck and apparent size of the root before dislodging it.
Sometimes, you will be fooled and find a small root under a large top. Think about it this way... will it be worth more on a dealer's grading table or right there in the woods making seed for a few more years while it gets bigger?
If you do dig out a small plant, you can normally plant it right back and it will be fine.