Advice/tips on changing a toilet? Grey water drain cleaners?

Thanks for the response. I actually found this videothat pretty much told me just about everything I need to know.

My issue with the grey lines is that the sink in the kitchen is draining pretty slow so I think I've got some build up. I'm not concerned with the tanks themselves, just the lines.

And do you know what the lines are made of? They aren't pvc, cpvc, or abs.