Modifying SFX.dat

I found an SFX file that uses LTTP sound effects, and I like it very much, but the water sound in it is the original LOZ one, and it doesn't loop and is very staticky and horrible and used everywhere in almost every quest. I found a good looping water trickle sound effect, but how do I go about replacing that sound effect in the old file with the new one?

Here's Freedom's tutrorial on how to do it: http://members.toast.net/mfreedom/ZC/sfx/sfx.htm

Thanks!