Depending on the number of teams in your league and your scoring, it looks like you did pretty well. If the risks you took (especially Nomar and Brown) work out, you have a stacked team. As to your questions:
Picking up another rp would definitely help. First, check the free agents in your league and see whether Looper is available. Guys like Gagne or DeJean might also help. If anybody with saves potential hasn't been picked up yet, pick them up and drop Lee (who I'm not terribly high on). Hernandez would also be worth dropping for a closer candidate.
If all the closers have been picked up already, a trade is a good idea. I'd start by shopping one of your 3b's and trading the one that you can get the highest return for (which will probably be Blalock, but you never know). The stock of your 3b's is very high now, and you don't need three - perfect situation to sell high.
Check out our sleepers list and the post in this forum for some comments on Ishii. I think his chances for success are good, but be aware that nobody knows for certain how well he'll perform.
Other improvements: Lose Lee. I like Nixon a lot this year, and even if he falters, you still have Jenkins. Pick up a backup at a position where you don't have that kind of depth. Otherwise, I don't see too many holes here. A little more speed would be nice, but you can't have everything...