The guide section for Postal 2 has some fantastic modding guides in it *O*; even though most are geared towards creating maps, there are some non-map guides too.

I wrote a guide about creating sound mods for the game, to replace sounds like npc voices, animal noises, weapon sounds, etc.

http://gtm.steamproxy.vip/sharedfiles/filedetails/?id=448550256

http://gtm.steamproxy.vip/sharedfiles/filedetails/?id=420457001

Here's a guide by J00sh about creating a mod in Postal 2 to replace the music files! I used this guide a lot when I made my music mods. Very helpful! c:

http://gtm.steamproxy.vip/sharedfiles/filedetails/?id=457643178

I wrote another guide about modding Postal 2 O:

This guide is about creating rexture/reskins for different things; like weapons, people, clothing, etc.