Heh, someone in chat just asked a very similar question regarding elevations. See if this helps any:
Technically you can have both building and grade elevations in one project. However, I personally like to have site and building in seperate files for ease of manipulation anyhow.
In regards to the file linking, it will be benificial for you to have 2 instances of revit open if you want to have both site and building files open at the same time for manipulation; Revit doesn't like opening linked files int he same instance of Revit if they are open as a link in a nother project (say that three times real fast!). Once you save one filel, you simply right click the link in the project browser > links section and tell the link to reload to see the changes.
Some hindsight insight for you. Once you have the links in the correct place, there are 2 ways to manage that location: Publish shared coordinates which requires making a separate location setting in each project (done automatically when you publish shared coordinates). The second method being to pin the links and threaten to chop off the fingers of anyone that moves it. Neither method is a guranteed way to keep the links from moving, but the shared coordinates will at least fgive you a reset value if someone accidentally drags the link.
Hope this gets you started! Best of luck!
Carl - rkitecsure[at]gmail.com
Need help? I'm probably in my chat room!
You fell victim to one of the classic blunders. The most famous is never get involved in a land war in asia, but only slightly less well known is this! Never go in against a Sicilian when death is on the line!