Does anyone here have experience with Game Extractor?

[gameripper]

I don't know what to tell you, man, they just didn't want to show up in the program.

So basically you're saying: "I did something but I won't tell you what because it's probably not the thing you told me to do and didn't work"?
Okay...

I managed to extract them in a somewhat convoluted way (unfortunately they aren't in the best quality)

DOS games never stored the entire music as PCM data like modern games, simply because there was not enough memory for that. They just stored music notes most of the time, so poor quality is most likely a result of an inadequate sound bank. Try converting with an OPL3 option, that was the de-facto standard at that time.

I've attached 3 ogg files in a zip, a DOS game's music file converted with 3 different tools and soundbanks. Just listen to them, how different their quality is!

Sadly, the only sprites I can locate are the interface and technically what could be classified as backgrounds, static images. The characters, buildings, and other map elements must be locked away somewhere among the code of the other files.

Spritesheets and maps being stored in a custom format is very very likely.