I have a couple of questions: * Will this old machine actually run 10.13 without blowing up?
If Apple support running the OS on the machine, it should run Ok. 2GB ram is a bit low these days, but then you will have problems there with any OS.
* If I install 10.13 over 10.9, will I have to uninstall and reinstall
MacPorts?
Yes. You always have to follow the migration guide when updating to a new major OS.
https://trac.macports.org/wiki/Migration Chris
