You are not correct. The entire light engine does contain the dmd board, but when they fix the tunnel, they just open up the tv, unscrew a few things inside the light engine, pull out the tiny light tunnel, put a new one into the holder and put it back together. No new light engine involved.
Back in the beginning of the light tunnel repair process, before they realized how easy and cheap it was to just replace the little tunnel, they were replacing the whole light engine. But it was with refurbished units which often were worse than the ones they replaced.
So anyhow, enuf Samsung repair history from me. But you won't get the whole light engine replaced anymore.