With no prior modding experience whatsoever, i have managed to figure out how to use Gimp and the downloadable skins from BattleFlags.net to modify the skins and conning tower to put my own battle flags on the tower. If you're starting from zero knowledge about this stuff it's somewhat frustrating, however, if you already have/know how to use photoshop or Gimp, you'll be way ahead of me. The idea of personalizing my sub was very appealing to me, so that was enough to light a fire under my ass to do it. If you use the battleflags skins they will point you to which files have to be modified, and you can just "save as" directly into the skin folder from which you got the tower skin from.
I got around the numeral reversal by using a the roman numeral V intead of 5
I used Tigershark patterns from a good pic to get the pattern for the tigershark stripes