2001 Millenia engine interchange info needed

I stumbled on this site while doing a search. Looks like a lot of great info. I am new here so bear with me.

I have a 2001 Millenia and just bought it. I got a great deal on it because it needed an engine. The engine is making noticeable knocking noises from lower end and top end. I pulled the front valve cover and it looks as though nobody has ever changed the oil at 41000 miles.

I am looking at a 2000 Millenia engine. Can someone tell me what engines and years will fit without too much extra work???

Thanks in advance

John