So I have a more or less functional quad and a semi functional rover. Every time I download firmware and even on the main catalog page for my quad kit they reference a "parameter file" but in all the calibration steps, configuration, etc. I've never seen any mention of loading this file.
What re these parameter files?
A parameter file is essentialy a configuration file. It is where the APM 'looks' to determine what sensors should be enabled and what actions it should take under certain conditions, for example what to do when it loses radio signal. Do you use the Mission Planner to load your firmware? If not you should download it and get familiar with it's use (it's easy). You can see all the standard as well as advanced parameters here. This is also where you can edit P.I.D. settings to tune the copters flight characteristics.
I don't have a multicopter myself so I can't really help you there but here's a link to the ArduCopter wiki page on the Mission Planner MP and here is a link to the Mission Planner wiki on the Arduplane page MP hope this helps.
Ok. I suspected as much. So the obvious follow-up is if I am using APM to load firmware and configure, what should I do with the parameter file that is published by 3DR? Is there some way to read it in and use it as a baseline? Reading it as a text file its too long to type in by hand.
When you go to the Mission Planner > Configuration Tab the go to the sub menu from the left pane 'Parameters'. Then in the lower left corner you will seed a tab that says 'Load'. From there you will navigate to where you have downloaded the parameter file you want to use, then click 'Write Parameters'. Now you're done!