What are some things I specifically need to be watching out for? I heard about Apex Seals, but is there any other way the previous owner(s) could've damaged the engine or other parts in the car without it being obvious or easy to detect?

 

you might take some time with the stickys.

https://www.rx8club.com/new-member-forum-197/rx8-faq-new-owners-116484/

the faqs, i know it would be stupid to look in that section.

beers