i just purchased a 2001 expedition (155,000 miles 5.4 v8 2 valve 4x4) to haul my landscape trailer and my growing family. The engine has a knock at idle. i have yet to actually drive it as i had it towed to my home. I have done some light research and i am still unsure if i need to drop in a new to me engine, rebuild it, or do i just need to do a simple fix?

 

It is always a good starting point to check the oil pressure with a reliable gauge.
Depending on what you may find there, could either suggest further tests/checks or provide sufficient info to make a decision then and there.