Not the whole trdata.narc; it's like, say if the trainer without the text is trainer #23 (starting at 0). In that case you want to replace trdata_023 with the original, then edit that particular trdata_023 back to having the information you want.
Yeah, that's what I meant. Indeed, the co-ordinates are nice. :3 The thing is, every time I try to change the script data by hex the whole lot goes kaput, so it's a bit of a risky business to be honest. You can give it a whirl but I wouldn't count on it too much
Oh, yeah, the line of sight thing makes sense, it's like that in HGSS too.