Hello there, and greetings from another Wisconsin'er to ya! Grats on your new Eagle, I'm envious
You had a couple of questions...Rear Endcaps you're talking about>>>Are EXTREMELY hard to find for SX/4's. There was a couple on eBay a week ago that went for $100 bucks each... It really doesn't matter for sport packages or not, they're just painted black and the chrome strip is painted red or white for the package.
There are no special sport floor mats, if the interior is black then it would have just regular AMC floor mats. Or...none at all if none were ordered for the car from the dealership.
If you would like to check the tranny fluid, it would be under the hood on the passenger side of the engine way in the back. You might have to push back some vacuum lines and some other odds and ends to be able to see the silver dipstick.
Your hatch is another thing... my friend has an '81 SX/4 Sport with the push button opening in the glovebox. His also doesn't work either, but what he did is make a long rod with a "poker" at the end and he goes from the front and reaches back there with the poker and sticks it in between where the striker sits on the post in the hatch, and turns it manually. He doesn't go back there much, so its perfect for him...but if I owned the car I would have it fixed, my OCD would be killing me...it would have to work properly... lol
But other than that, I don't have experience with fixing it, more research would have to be done!
Have a great time with your new Eagle, and don't let it get exposed to Wisconsin winters!!! Or at least not too much
My Eagle and I sure do love 4-wheeling in the snow...