As I mentioned in my previous post, you can use any hex editor, and the advice given here to do it. There are several free hex editors you can easily find and download, although you'd have to consult someone else if you wanted to know which is best. I've only ever tried one, and I don't remember where exactly I found it.

As for TECjcs, or a similar program more specific to .j2l's, I unfortunately can't help. I don't have anything of that nature myself.