If you want to do a Colin Edwards 2004 bike, I'd wait a while. Tamiya are bound to release a '04 RC211V sooner or later. It'd be much easier than converting.
As for changes, later in the season, all the Honda bikes got a new exhaust configuration (I think Barros first used it ate the Sachsenring, and it got introduced to the other bikes later.). You can tell by the way the upper exhaust exits are more faired in, and the lower exit doesn't have the big silencer on it (they actually used this late in '03, but it's not in the kit.).
Here's some pics comparing the two bikes:
'03 bike:
'04 bike:
hope this helps.