Hey all! Really hoping someone can give me guidance here.

I have a 2016 Mazda CX-5 AWD that I purchased used around 9 months ago. Unfortunately it was running on low oil for too long (stupid I know) and the engine is completely ruined. My car broke down in the mountains about an hour and a half away from where I live so I am having to communicate with this mechanic all over the phone. This kind of sucks and I am a little skeptical about a few things. The engine they quote me for is around $2,000 and has 78,000 miles on it. I believe they are fully assembling it. After asking for the VIN they said it doesn't come with one? I also asked for some documents that prove the engine's mileage and that it was tested and they also said I probably won't get any of these? Does this seem weird? The told me the company this engine is coming from is LKQ which seems like a legit company but again, this is all verbal and I have nothing that proves this.

If anyone has experience having their Mazda engine replaced I would love some tips on things to watch out for/things to avoid. I really want to make sure I am not screwing myself over here.

Thanks