I dont think it is wise to leave it up to Rolen to get your 3B position squared away, and there is no replacement for a 3B with his capabilities outside of Zimmerman or ARod. If there are other 3B available to you, look into those if you make this trade. Someone like Freese or Roberts will at least get you solid avg numbers. You do have Lidge coming back at some point, so you have a RP in waiting there, but Street is hard to part with because he is as dominant as they come at RP when playing (I know, I know...injury concerns and all. They arent predictable so I dont really buy into it that much with the way hes pitching now). I absolutely think you need another competent SP, so Ubaldo is nice. Crawford will turn it around no doubt, so no worries there. Ellsbury is gonna be huge for you, you dont have any real SB leaders on your team, and I think those 3 guys help your team more than getting the other 3 guys will.
If you can get Buchholz for Abreu, please by all means try that out first, I would get rid of Abreu anyways, but Buchy can really help you out in the long run.