1)After you make changes, then save the reference project, the nested veg. will update in your master project. If it is a different length, then a notch will appear along the top edge of the event to indicate the new boundary. Just trim the edge to the notch.
2) You can tell if any media that is/was part of your project is currently on the timeline by checking the details view of the Project Media Tab. The second column is Use Count. Anyhing with a 0 is not on the timeline. You can sort by this heading to group all with the same use count.
Also, Excalibur has a Find Unused tool that will create a new track and place all your unused media on it.
Gary Kleiner
Learn Vegas and DVD Architect
http://www.VegasTrainingAndTools.com