I'm looking this cassette, and it has splines for the spline tool. Also, there are notches inside the first ring for a wrench. I have a chain whip, soon to have the spline tool. My question is this: Is that first ring "lefty loosy" or opposite of that? If I'm not mistaken, when I get that first ring off, the rest of the cassette should slide right off. Is that right?

All of Shimano's cassettes have a lockring that the splined tool fits into. It's seperate from the first (smallest) cog. Use the chain whip to hold back on a large cog (better leverage) and unscrew the lockring (lefty loosey) with the splined tool. That's all it takes!