EDiT: This game has crc check of files, when you replace original zip with modiffied, game after launch re-download new one. Even if you change only one byte in original
Yeah thanks I noticed that, so I put "read only" on zip-file I currently work with. Btw, is that possible to turn off that crc-check somehow?
Ok, I successfully renamed the header with FWS and open it with Flash, and there I just found some red squares in it and then deleted them.
After that I replaced the original file with updated one (also changed back the GFX header, etc). but when I open game now - almost all interface is missed (radar, character's avatar, etc) which is not bad actually, but in same time the rest of interface doesn't work at all either, nothing happens when press ESC button or when trying to change weapons, etc... just nothing, but I still can play with a character though, jump, run, etc.
I also tried just modify the textures by AceWell's method (thank you again

, however, got the same result as described few lines before - even if only one texture is modified, all radar is missed completely along with few other parts of HUD, and nothing else works... OMG this problem turns into a huge quest for me... :-\