An error restarting indicates a bug in the GetIt code, since the plugins are installed via GetIt and aren't active (aren't loaded) until the restart.
Not fully. They are part of the standard IDE build, but are still separate DLLs (not BPLs.) Both plugins use a powerful editor API for all their drawing which is located in CoreEditor.bpl, which I built, and which is what allows them to figure out what's onscreen, where, at what line, etc. We're planning to build an API like this into the IDE, and then move the plugins to use our inbuilt API, at which point they'll be fully integrated.
Ultimately we would like that API to be public, part of the ToolsAPI. Bookmarks and Navigator obviously benefit from it, but other tools like GExperts and CnPack also draw in the editor. We have to be careful since we don't necessarily want doing this taken lightly, but making an API available is a better choice than plugins writing code to hack in the same functionality.