In short, yes, that's all you need. More concisely, no.
Your grape juice will ferment - it'll take about a week with champange yeast, maybe 2. It could probably do with a cup or so of sugar to make it stronger. Put a ballon with a pin hole on the top to allow gas to escape but no contaminates to get in.
After a couple of weeks, put it in a different (sterilised) container to move it away from the lees, and leave it for a couple more weeks.
And that is the very basics of wine making.

Feel free to correct me if I have missed anything.
Dicky.