For a first time draft, you did pretty well
VMart, Hafner, and Aramis are a pretty core for an infield. Your OF is interesting: if Guillen isn't a nutcase this year, he could do some damage, and Cabrera will put up monster numbers this year. Your bench for offensive players is a little weak, but as long your starters hold up, you should be fine.
The SPs are solid, especially Oswalt and Perez. You're correct that you need a closer, but you can always try to search for a cheaper one as the season progresses (no need spending excessively). In terms of steals, there may be a low-end, free-agent type guy out there, like and Alex Sanchez; I think that Izturis, if you ever play him, will get you a decent # of steals though.
Check out my team at:
http://www.fantasybaseballcafe.com/foru ... hp?t=98508