Well mechanic says I spun a rod bearing and that it’s better to get a new engine should I look for a new one or try to rebuild it and if so what all would I need? Engine will still crank and start just has a knock

 

If you have never rebuilt an engine, it may take time as you acquire new skills and tools. So you need to think about your timeline. If this is your daily driver, how long can you go without it?

If you pick up a "new engine you will need to consider the source. And if you have never pulled a engine and replaced, you need to consider that timeline for the same reasons.
Then you will have your original engine to rebuild at your leisure.

The fastest fix is to dump cash and let a reputable shop do it all.