Isn't triangulation of all faces a native feature when you export your Sketchup model to Collada? Normally, it should be available behind the 'Options...' button in the Sketchup 'Export Model' dialog.
Next, there are indeed separate extensions that offer similar functionality, but these may be beyond your needs. So, best is to start with the out-of-the-box feature, and see how it works for your specific requirements.