Do I need a new engine for '82 300SD?

My dad had it in his care and forgot to torque down a drain plug following recent oil change. While I was cruising down the freeway I payed no attention to the oil pressure gauge. Plug fell out, oil was lost. The car came down to a stop. I estimate the motor ran dry for about five minutes. It will start with a moderate pinging and while cold will maintain oil press. But once warm, pressure drops to nil, noise increases considerably untill it just dies. Turbo spins freely.

Do I need a new engine, or can a new oil pump be the fix?