I'm not exactly sure what you are asking to do when you say "Add weight/mass information to the model"
If you mean that you want to "pull" the information, you can go to Tools > Mass Properties. Be sure to set the density to the density of the material that the part is made out of.
If you want to add it in as a property, you go to File > Properties and navigate to the "Custom" tab where you can add any number of properties.
If you want to have a "sensor" that alerts you when your model is out of your tolerance values for either Mass or Center of Mass, you set up a "sensor" by right clicking on the "sensor" folder in your feature tree. If you don't see that folder, you right click in your feature tree and navigate to Hidden Tree Items > Hide/Show Tree Items and "Show" the sensor item.
You can make a macro that gather's the Center of Mass info and adds a point to the model in the location of the Center of Mass every time the model Rebuilds (or every time it is initiated). You can also make the same macro display a dialog of the mass info.