How do i change the animation/sprites of the vulture's grenade explosion? does it use jpg or png images?

In Iscript, the vulture grenade explosion is entry 440 in Images.
The image format is .grp, but I don't know much about image editing.
Just...if you use .jpg, you will be cursed👻👻.

The SC sprites are .grp (1.16.1) or .anim (1.18 onward) files. Both are convertable to the mundane file formats (.bmp or .png) respectively using PYGRP - found in the same PYMS suite that you are apparently using - or Animosity. The latter utility has a thread (with download links) here: http://www.staredit.net/topic/17590/

If all you need is changing not the image itself but the way it works, yeah, Iscript is the thing to go for.

I opened a few .grp with PYGRP, Animosity cant open them even though it has the option to. I want to replace the image of the explosion, i dont know where the original image is located tho. I looked inside broodwar.mpq, starcraft.mpq, broodat.mpq, patch_rt.mpq.

It's in StarDat.mpq, unit\thingy\efgHit.grp