I went there about 2 years ago. The results are at:
The place is huge and I'm sure I wasn't even able to see half of it. There's a lot of stable elevated platforms if that's what you're looking for. There are also a lot of things that look very rickety so climb on something at your own risk. It's probably one of the more dangerous places that I've done some photography at. There are a lot of things here that you can injure yourself on if you're not careful.
Technically, you are trespassing. It's surrounded by a chain link fence that it easy to get by. It's best that you do not park your vehicles at the main entrance. You don't want anybody to know that you're there. It's easy to get in and attracts a lot of curious people, but if you're there, you're there illegally. You probably won't be bothered, but be aware of that.