If the live rock stinks it is not cured, if it does not really smell it's probably cured.

Also, if you are getting it from a LFS it's probably not cured. If it's from a fellow reefer it's probably cured but may have die off depending on how long you have it out of the water.

It's good practice to throw it in a bucket with some saltwater for at least a couple of days...this way you can inspect it and make sure you don't have any unwanted pests headed to your display. This will also give you time to determine if it's cured or not. 10 pounds of live rock will make a significance in a 29gallon system.

In a 100 gallon system you'd never notice it...but a 29gallon you need to to be careful and monitor your prameters closely.