You can read more about disabling plugins here: Disabling ruby scripts | SketchUp Help. I fink it’s wise though to keep the code snippets somewhere in your computer as a future reference (the website may change and the link be broken).
You can press arrow up in the console to get the previous command back, but only within a SketchUp session. Here is more info about the console: http://developer.sketchup.com/en/content/ruby-sketchup.
