All the Carves were pretty good, so 2004 is just fine as your first small board.
Yes, there were some minor "improvements" from 2004-2007, but until you have quite a bit of time on the 2004 board, you would not be able to appreciate any of the little things that make the 2007 board better.
One of the things that make the 2007 board better is the fin.
Here's the spec's on the 2007 Carve 111:
Carve 111 111 247 65.5 43.3 7.2 6.9 4.7-7.5 Freeslalom Swift 360 30-40
Here' s the spec's on the 2004 Carve 111:
Carve 111 111 259 64.0 40.1 6.6 7.2 4.8-7.2 Tuttle box Drake Freeride 320
So, for 2007 the width was 1.5 cm wider and the 1 foot off tailwidth was 3.2 cm wider, weight was about the same.
BUT, the slightly wider 2007 Carve came stock with a 36 cm fin.
So, the 38 cm isn't going to be "too big" and if you want to put a larger rig (perhaps 8.0 m2) on it to get better light wind performance you will already have a fin for that.
I read your post on rec. WS and I agree with the guys there as well.
It might be better if the dealer could find you a 36 cm fin (vs 38 cm) but you are soon going to want a 30-34 cm fin for your smaller rigs in higher wind conditions.
I used to use the 32 cm fin from the Carve 111's I had as a "big fin" in the Carve 99's I also had as the stock 28 cm fin in the Carve 99 just wasn't enough for the 7.5 Retro.
Even the 32 cm Drake Freeride was a little on the small size for a 7.5 m2.
The 32cm really was "sized" for the mid range sail sizes on the Carve 111 (in the 6.0-6.5 m2 range).
Hope this helps,