It's a nice team, especially your offense. A nice balance of power and speed. You could definately trade a 2nd baseman and get a good pitcher in return. I'd trade Giles. Kents value has never been lower. But trade whichever you can get a better deal for. Keep your OF intact unless there is a good deal. They will put up very good numbers all and you'll be able to get more for them a month in. I'd trade Kearns after a month and he's leading the league in everything, personally. The injurys are piling up, you know?
Anyway, pitching. Solid, though chancy. Oswalt, Brown, and Beckett have all missed serious time in the last 2 years. Jackson and Harden are promising but largely unproven. I would try and package something like Cabrera/Harden for a studish pitcher.
Your closers are terrible. Neither has experience, which you know, and neither is all that good. Nathan had a good year last year but I'm not a believer in him (due mostly to his era in the high 4s during his 8 year minor league career). Rhodes is getting old and has failed in every chance he's been given to close. If you want to compete in saves, you'll need help here.
Trade a 2b (Giles?) and a 3b (Cabrera?). Patch up your starters. Get a good closer. But you'll be fine even if you don't do these things. It's a good team.