1. Not sure if you specifically need mirc, but you do need to be in their "room" to get FTP access. 2. No, xbins is not illegal, and there is nothing illegal there. Some stuff that may be a little grayish, depending on who you ask, but there's nothing illegal. What there is is a great collection of apps, exploits, dashes, some homebrew games, emulators, and that sort of stuff.
No, xbins is a right place. For instruction to download there, follow the link in my sig. Then look for #xbins. Just do what guide said.