Yeah, I got my Wii on release, and I don't use the SD card for anything yet. Lots of room.
Now, if you download LOTS of Wiiware games, you can store them there instead of re downloading them, but you can't actually save anything directly there. You only interact with the onboard memory.
You can get the component video cables for $10-20. A generic set is fine. They help in picture clarity a little bit even without 480P, but 480P does look nice.
I got standard rechargeable batteries for the Wiimotes, $30 in total expense (For 1 charger and 2 sets of 4 AA, I did have 1 charger already though), and they work just fine. You can get almost 30 hours out of a normal battery set with the Wiimote (less with another accessory attached as well, Classic or Nunchuck), so you don't need the little recharge kits.
However, I think you can get a combo pack that comes with 2 chargers and a charging station, an SD card, HD cables, and a few other things for like $50 at Target.