Study how hex editing works, check my "how to make a new region" tutorial in Skeetendo Inc. Next compare the data mentioned in the offsets of that tutorial by viewing them with your own hacked rom and an original gold/silver rom, and see what is changed between those two. Change the bytes of your hacked rom back to "normal" (or what they are in gold/silver roms).
You can compare the datas easily with "copy --> paste" functions of the hex editor without knowing much about what you're doing there.
I can do hex but its very hard for me. I'm much better with tools.