ok i figured out how to edit the pla trainer icon if anyone else ran into the same conundrum as me.
load up the save in pkhex>block data>export blocks to folder. from that dump, all we need is the "F25C070E.bin" file. open that up in HxD and the byte of interest is at offset 0x3C. i dont have documentation of all 8 possible choices, just the 2 i tested, so i recommend making a new save file with your desired gender/skin then playing until you get your galaxy expedition uniform (~30mins) and do the steps i listed earlier to this save as well to see the correct value you need to switch the byte to for your desired outcome for your main save. once you replaced the byte with your desired value, save it and make sure its the only file in it's folder. then from pkhex again, click import blocks from folder, then you should be done and good to save
this took quite awhile to find the correct file but everything seems to be working fine. and for the record i'll just list the 2 values i know while figuring this out for my save:
Default Skin Female: 02
Tan Skin Female: 07