How do I replace the gasket on the Portafilter?

I actually have the Starbucks (AKA Saeco) Profi Estro. The filter basket gasket is shot. I purchased a replacement but don't see any easy way to replace it. (It has a groove in it that requires dismantling the basket assembly to fit it in). Does anyone know how to take apart the handle/basket assembly, preferably with pictures?