Hello Boobear,
Just gimp scripts are like photoshop actions in a way, but they are also very different since you have to create them by coding them, as opposed to photoshop actions where you save your "steps as you go".
Basically to install a gimp script, you just need to put it on a location where gimp can find it.
To find the location to put them go:
File->Preferences->Folders->Scripts
Here is a website with gimp scripts:
http://registry.gimp.org/
- Norma