FreeBSD, Ports, and MySQL

So I’m pretty good with *nix systems, but I’m not that familiar with the FreeBSD ports system. I have a machine here that I need to upgrade MySQL from version 4.1 to version 5.0. Am I correct in thinking that I have to deinstall the version 4 port and install the version 5 port? Is there an easier way to upgrade?

Also, I’d like to know what programs depend upon MySQL before I change anything. I tried using pkg_info -r and pkg_info -R but they both listed nothing. Is there another command I should be using?