Низнаю, никогда не делал свой патч. Но для изменения некоторых звуков, моделей, интерфейса я всегда юзал программу "Ladik's MPQ Editor" совместно с "Rena!ssance Users Choice". Результатом доволен)

если умеешь C++ или C#, ищи либу Shadowflare MPQ API

Function SFileOpenArchive opens a MPQ archive for reading.

BOOL WINAPI SFileOpenArchive(
const char * szMpqName, // Archive file name
DWORD dwPriority, // Archive priority
DWORD dwFlags, // Open flags
HANDLE * phMPQ // Pointer to result HANDLE
);

Parameters
szMpqName

[in] Archive file name to open.

dwPriority

[in] Priority of the archive for later search. StormLib does not use this parameter, set it to zero

dwFlags

[in] Flags that specify conditions for opening the archive. They can have these values:

SFILE_OPEN_HARD_DISK_FILE - This value is used by Starcraft but does not seem to do anything different than any other values. If this is used, the function will open the archive without regard to the drive type it resides on.
SFILE_OPEN_CD_ROM_FILE - This causes the function to only open the archive only if it is on a CD-ROM.
StormLib does not use this parameter, set it to zero.
phMPQ

[out] Pointer to a variable of HANDLE type, where the opened archive handle will be stored.

Return value

When the function succeeds, it returns nonzero and phMPQ contains the handle of the opened archive. When the archive cannot be open, function returns FALSE. More informations about the error can be obtained from return value of GetLastError().

пишешь патчилку вручную

Absol, "Rena!ssance Users Choice" скачайте и попробуйте ЧТО ЛИБО сделать. Если поймете принцип работы.