My 2002 Nissan Pathfinder 171,000mi shook violently and the engine lite blinked on/off. Afer parking it seemed ok, but I took it to Nissan for a check. Then after they replaced the spark plugs the engine locked up. They found that cylinder #6 was nearly full of oil. They suggested that engine replacement would be better that trying to repair as the cost/labor to repair the cylinder may cost a little less but there is a possibility that more damage may have happened to the engine.
What is a typical repair cost to get oil out of a cylinder after engine has lock on 2002 Nissan Pathfinder
It is more likely the engine filled with coolant from a blown head gasket unless it filled with oil due to a huge internal mechanical failure in which replacing the engine would be more viable. Check the value of your truck first before making a huge investment.