PO refers to a "previous owner". I'm not so sure your Universal is necessarily a replacement. Many did have the Atomic 4, but I think some came with diesels, especially in the later model years. The '73 P30 I had was powered with the Universal diesel, and as far as I know it was original. It's a good motor, simple and reliable when maintained, and adequate for the boat.
As for the handling of the P30, I imagine you'll love it. It's a very responsive boat, and fun to sail. Mine was tiller steered, which is a blast on this size/type of boat. Gives you a great seating position and control when sailing, and stands out of the way at the dock or at anchor.
Items to check include the hull/deck joint (can be damaged by impact with pilings etc.), and sloppiness in the rudder post. Worn rudder bushings are somewhat common, but easily replaced. Also check for moisture in the deck near the chainplates.
If you haven't read it, check out this review: BoatUS.com: Boat Reviews by Jack Hornor, N.A. - Pearson 30