Best to ask questions on the NG dedicated to server,
microsoft.public.project.server.
That being said ...
Project files cannot be accessed/edited from SharePoint. SharePoint is
a separate product. However, Project EPM uses SharePoint as one of it's
components in the EPM suite of tools. Project Server and Project
Professional are also required, as is a number of other things, e.g. SQL
Server, a Windows Server, web server, etc.
I understand that there are ways to make Project EPM work on top of
Small Business Server if you don't want to put it on its own separate
Windows Server. This was discussed in these newsgroups a few months
back. Search
http://groups.google.com to find the discussions.
See
www.microsoft.com/project, section "Planning for your EPM Solution"
some documents you should read.
Remember that the computer systems side of implementing Project EPM is
the easy part. Much more time/expense will be spent on the people systems.
Hope this is useful to you. Let us know.
rms