Would you buy a 370Z with a replaced engine?

[STB370Z]

Hey guys,
I'm hoping to be a proud owner of a 370Z sometime soon. I've been looking around at various used ones and nothing's quite worked out yet, but I've come across an interesting candidate and would like your opinion. It's a 2009 370Z with 25000 miles, BUT the engine was replaced by Nissan at 18000 miles. What do you guys think of this? Should I just ignore it or pursue it... The owner claims he was able to convince Nissan to change the engine because the "crank and speed sensor" went bad and he wasn't sure what other damage could have been done to the car....Does this sound reassuring to you guys? He seems like an honest enough guy and even if the story is legit, the fact that many parts were disconnected/removed, the engine unmounted, then everything being replaced/reinstalled has me feeling a little uneasy, I've had some bad experiences with dealer mechanics and know that quite a few of them could care less about doing the job carefully or even fully correctly... On the other hand, he has driven the car for the last 7000 miles since the engine replacement and claims it runs perfectly (but of course, he wants to sell the car, haha), so maybe I'm overthinking it?

Anyway what do you think? Thanks!