I created a folder called "Sims 3" on my D: drive, and when I installed from the DVD's I created new folders for each of the EP's and SP's. You will have to manually change the destination for every SP/SP you install.
All the CC and downloaded content goes into the Electronic Arts -> Sims 3 folder in Documents on C:, same as where all your saves, screenshots and the rest of those folders are. That folder has to be on C: and will automatically go there even if you install the game on D:.
I installed my game recently and asked questions on NRaas:
https://www.nraas.net/community/chatterbox/topic7827
https://www.nraas.net/community/chatterbox/topic7840
Remember to deny installing EA Download Manager and Origin.
