engine rebuild parts

So my sister has a MS3 that she loves so much but had a problem with the engine I’m not 100% on what happened but the engine is done for we are looking to get a “new” used engine with around 60-80k miles. Where should I look to find one? What should I look out for when looking at engines. If...

Looking for a must replace parts list on this forum updated to this years parts and prices. Also the parts that are available as far as head stud options and internal parts that you guys suggest from a mild build to a major build. Thanks.