You must be getting pretty excited!
Water hoses: get yourself a hose for drinking water. They sell them marked specifically for that purpose.
(You'll also need a hose for washing stuff down, but that can be purchased just about anyplace...)
The Slinky...
I assume that you've got the lug-style connector: any hose equipped with the same connectors will fit...
If you buy a hose kit: make sure that you've got a 80 degree fitting with it. That's the one that connects into any campsite sewer system.
I bought one of the sewer hose "cradles", that sort of helps you keep a proper downward angle from the rig to the sewer system: it has served me well.
The rig should of course come with the correct power cord for hooking up to "shore power". You shouldn't need anything extra for that...
Let us know how the delivery experience goes, and good luck!