“Wouldn’t that cause you Google troubles?”
Yes. Google says a person can do “almost nothing” to hurt another site, but linking to a domain can hurt it, hurt its topical theme, and especially if say an innocent site has thirty links to http://www.site.com, and some bad person make 10,000 links to site.com On the other hand, that doesn’t make the pages disappear, just maybe make site.com rank higher, which would then actually not be a negative.
I’m not a tech guy, so I won’t try to tell you how to do a 301, but using .htaccess is correct
You could no index integrity-casino-guide.com, or you could just put up a page that was completely different than what you have on the main domain. Perhaps a good idea for you would be to put up a near blank page with just a single link to your main domain (so anybody ending up there can get to the right place and any PR you have going to the old one is sent on too). I’d then link to this new page on the old domain, so Google sees that the content there now is completely different than what is on the main domain.