Let me just mention one important thing, before you come back with a 'My wireframes are :censored:ed up!!!!11111" topic, ok? (And I know you
would come back with such a topic, since every1 starting working the wireframes out does =)).
Simply editing the wireframes and putting them back in the GRPs will do you no good, because they will appear all screwed up in the game. If you don't believe me - just try it. What you need to do is save each of your modified BMPs with PSP's 'Batch Conversion' feature, and using the 'RLE Encoding' option.
Here is a similar thread from SME, and I think you should check it out:
http://www.smempire.org/forums.php?action=viewthread&id=2139