Actually, this is not quite true, the true answer is: As long as the LCD screen can accept a VGA connector, then it will work.
All early PS/2s have a video controller built-into the motherboard. In his case, he didn't specify whether he had an original Model 30 or a Model 20/286. It would not matter in either case because the original '30 used MCGA controller and the 30/286 used a VGA controller, but both used a VGA connector. Some later PS/2s have XGA/XGA-2 controllers built into them or come with them as a MCA card. In short, he should have no problem.