Yes, the fire hydrant is separate. It looks like there are some deals on the web. I probably won't do the synthetic grass, and I'll be getting the smallest size (or maybe the 2nd smallest).
I think Thor will probably be okay with it because he likes peeing on grass, and it should smell different from anything else in my apartment... but yes, it's possible it won't work. I have some "mad money" that I'm looking to spend on something frivolous.