Assuming you're talking about Project 2003:
1. You only need Pro if you are going with Project Server. Otherwise Project Standard 2003 is quite sufficient.
2. Yes, easily done but there are some caveats. The technique is to use a Master Project. To do this, simply open a new blank project and click on Insert | Project and navigate to the project you want included and select it. Repeat that process for each project file you want to report on.
You can either link to the project (by leaving a checkmark in the box labelled "Link to project") or you can copy everything from the project into your Master project (by clearing that box).
If you are going to get the most out of a Master Project, you need to make certain that everybody follows certain conventions. For example, everyone needs to use exactly the same name for a particular resource. If one project has "Mary" and another has "Mary Brown" then you will not see the overall effect on her availability.
You also need to draw up certain ground rules about who has reponsibility for updating project files. The best rule: one file to one person. That person is the PM. This also means that the person preparing the Master project will not update anything. If you have linked to the files then you have to make certain that you don't save the inserted projects.
You also have to make certain that everyone is following exactly the same processes for updating the individual tasks. For example, how will you track %Work Complete? how will you adjust Finish dates to reflect early/late tasks? The answers to those questions, in turn, will guide you in establishing procedures for individual resources to report their progress (or lack of same!).
Finally, you need to be very sensitive to the fact that this kind of reporting will expose all PMs to much more scrutiny than in the past. Their reactions are predictable: they will do everything to make sure their projects are seen in the best light. If one project is falling behind because a shared resource is not being made available to the late project are you prepared to do the right thing: come down hard on the PM with the on-time project because her "resource hogging" has occurred at the expense of another project?
It sounds to me as if you are starting down the path of a PMO. Done correctly, a PMO can add considerable value to overall project management -- but without proper executive sponsorship and authority, it can be a frustrating experience.
