The trick is finding his agent. Pretty much all business arrangements need to start there. If he has an official website, there is probably contact info for his agent there.
In my experience, you will likely make all arrangements through his agent and/or manager, and not communicate with the artist himself until he arrives at the event.
I’d book him as a babyface-in-peril, prolly have him get beat down by Ricardo Montalban and get stretchered out of the arena. The next week, I’d let him cut a promo about how he’s been injured, but he’s got a mystery opponent to get revenge on Montalban, inside a steel cage, at the next PPV. The mystery opponent will be a vaguely familiar masked man, selling big in the early parts of the match, until his shirt is ripped…at which point, he’ll unmask to reveal Shatner. Violence ensues. Both guys blade. Kirk goes over, but Montalban has a foot on the ropes to keep his heat.