If I'm understanding you correctly, what I said above will work, or alternatively, you can also directly change the dimension numbers in Brawlbox upon texture replacement, and then just export it after importing it and, it should change the size
If by pixel size, you mean resolution, MS Paint, GiMP, or Photoshop are all well known programs that can easily do this; if this isn't what you meant, would you mind showing a comparison of what it is and what you're wanting to turn it into?
What do you mean by "reskin"? Do you mean rigging a character to a Super Smash Bros. character? Do you mean porting a character model onto a different character's moveset? Do you mean the general thing of how to install mods?
If you click the link to my website, it has a link to all of my current tutorials; one that'll sorta kinda show importing, cause it partially uses it, is going to be uploaded fairly soon, and then the full importing tutorial is coming much, much later
Also, would you mind posting a screenshot of what you mean?
Open Zero Suit's pac/pcs file, expand the MDL0, expand the Materials folder, and there should be a material named that; click on the material, and in the right pane, scroll until you find "Shader" to see what shader is associated with it, and then export both the material and the shader, and then Replace the ones for Wolf's fur materials with those ones; You can check which polygons contain fur, and then if you expand the Objects folder and scroll to OpaMaterial and/or XluMaterial, you can check which materials are associated with those polygons
Ok, just tested it, and for me, in .71, looks completely fine, but in .77, same black dots as you; it should still work fine in-game, the latest versions of Brawlbox are just a little glitchy with rendering, mainly because of a glitch with color nodes, but in any case, it's a Brawlbox problem; use .71 to view it if the black dots are too annoying