@desiv
Here is a quick reply as my time is short atm. Wheels is indeed an upgrade for Geos by Maurice Randall of Click Here Software. It is commerical, but has not been easily available for some time as Maurice has been missing in action. As an upgrade it is quite impressive. Geos had one single fixed window, Wheels has multiple windows thar are movable and resizeable. While Geos did have 3rd party patches to support expansions, Wheels supports just about everything out of the box. Having a 16MB disk image to work out of for drive A, 4 drives total, a 16MB RAM Disk and 20Mhz accelerator makes for quite a pleasant experience. My problem with Geos back in the day was running on a 64 with one or 2 1541 floppy drives was a painfully slow experience. This is quite the opposite. Even Geos games are improved, let alone the quality (for their age) applications. I plan on making a Youtube video soon.
No, there is no MP3 player for Geos to my knowledge. If you saw a mention to "MP3", that refers to Mega Patch 3, which was a competing Geos desktop upgrade.