There are major changes that just generally make this adaptation better than the actual film. With the exceptions of Beast Man and Blade, the characters are drawn like their toy counterparts, not the movie versions.
For those of you that haven't seen the movie recently or ever, here's a brief summary (the comic is almost 50 pages, so I won't go into too much detail).
Skeletor has finally got his act together and conquered Eternia. Meanwhile, He-Man rescues a Thenurian named Gwildor, maker of the Cosmic Key. It turns out that this was the device that finally allowed Skeletor to conquer the city Eternos.
They go to Grayskull, where Skeletor is, but end up having to use the prototype key that Gwildor has to teleport out, ending up on Earth. There, they meet two teenagers named Kevin and Julie (who has just lost her parents to a plane crash) who found the Cosmic Key.
A small team of Skeletor's greatest warriors go after them, and eventually Skeletor's whole army follows. Soon, they end up back on Eternia, save the Sorceress, and He-Man and Skeletor do battle on top of Grayskull.
Skeletor tricks He-Man, sending him over the edge, holding on for his life. For a moment, it looks like he will win, but Evil-Lyn throws a rock at his skull, sending him over, too. He-Man catches him and offers peace, but Skeletor refuses and falls to his death (apparently).
Later, Man-At-Arms comes from the depths of Grayskull, revealing a NASA and US flag. The NASA flag has on it, "Starfinder 5. July 10, 2221," revealing that the first humans on Eternia were from a future American space mission.
Gwildor offers to return them to any time they want, but they just want to go home. They end up arriving just before Julie's parents died, and Julie stops them from leaving on the plane.