If I download and install this on my SharePoint 2007 Server, will it overwrite anything i.e .Net files or current databases, or instances
No. If you just install Management Studio nothing will get overwritten.
Alternatively if you do not want to interefere with your SharePoint machine install Management Studio on a workstation you can remotely manage SQL/SharePoint with. Management Studio does not have to be installed on the same machine as SQL.
Joie Andrew
"Since 1982"