The 84-year-old Playboy founder has his marriage plans marching along smoothly; it has now become known that he is going to marry Crystal Harris, 24, on June 18, according to a Playboy rep statement. It will take place at the Playboy mansion and is supposed to be a rather modest affair. Hefner wants it to be “intimate” and “something very personal”. UsMagazine had it from an inside source that under 300 friends will be invited to the nuptials.Meanwhile Harris is faced with a bride’s one important problem, the choice of the gown. A Romona Keveza strapless dress is rumored to be under consideration. A ring worth $90,000 the lucky Playmate already has on her finger.