No, but it might if something other than an int3 were used. The particular byte value being written actually matters on some Intel processors. You have to first

No, but it might if something other than an int3 were used. The particular byte value being written actually matters on some Intel processors. You have to first put 0xCC over the first byte of the opcode you want to modify. You can then freely mess with the rest of the instruction. After that, you make the first byte be what you actually want. There is a discussion about it on the linux-kernel mailing list. Maybe you can find it.