I finally found an MD portable at the Hard Off in Funabashi! That video is here for those interested.
It was a Sharp MD-ST800 (2002) in great shape and was a great deal as an untested unit for just 1,100 yen (about $7)!
Though I call these players "upside down" ones based on how they are oriented, they work fine and are decently reliable since they were made later in the MD lifecycle. Sure, they're plastic-y but they are light enough and come with a backlit remote and charging dock. I particularly like the red one!
I was able to test it at the store and it worked just fine, so let's open it up and lube it since it is more than 20 years old!
There was no service manual that I could find online, but it was easy enough to figure out. Please check out the video and I've included some notes and screenshots below.
Thank you for your support and love of MDs!
First start by removing the battery door and just 2 external screws:
Then 3 screws on the inside of the lid - there's one peg we will angle the door off of after removing the 3 screws
Next we'll have 4 internal screws to remove: top left corner, bottom left corner, top right corner, and the eject slider in the top center.