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After installing the M2E plugin, you can go to Window - Preferences - Maven - Installations and configure external directories that contain alternate versions of Maven you may want to run in batch mode to build different projects. The interactive and Eclipse integration features of M2E do what they do and are largely version agnostic.
There are several configuration options that are best set immediately, before loading any projects. Go to Window - Preferences. In the Team area, select Ignored Resources. This exposes a list of file extensions and directory names of things you do not want to be checked into SVN. Click the Add Pattern... button and add "target", the name of the directory that Maven uses as a work area to collect the compiler output and generate the artifact. If you want to use Yale recommendations (at least for this workspace) that you only check in the Maven POM and not check in the Eclipse project files, then add the three Eclipse names ".project", ".classpath", and ".settings" (note that these names begin with a period but they are names not extensions so do not put a wildcard in front of them).
This is also a good time to go to Java - Installed JREs. Eclipse automatically adds whatever version of Java is the primary (generally the lastest) on this operating system. If you want to build for a different release (CAS is typically one release back from current) then after you have actually installed that version of Java on the machine add it to this list of Java versions Eclipse knows about and set the checkbox so it is the default.
One last point. Eclipse has been known to go into a very long loop screwing up validation of the HTML and JSP pages. To avoid this, you may want to click Validation and click the "Suspend all validators" checkbox.