I would absolutely take this trade. I consider Utley the #1 2B this year in fantasy (this, as a major Ian Kinsler fanboy). With losses & CG as stats, Peavy is not all that appealing to me. RBI & HR are not going to be your only boosts. Utley is an excellent source of doubles as well and disciplined enough to be a pretty good source of BBs.
On purely a value basis, I prefer Utley over Peavy. However, I don't think the trade makes sense for your team.
First of all, you just don't have the depth at pitching to let go of Peavy. You would be left with CC and Billingsly (not bad for a 1 -2 punch) but then your rotation would be very hit and miss. You would be putting yourself in a situation where you would have to turn around and trade Pedroia for another SP, and there is no guarantee you would get fair value in return. I've learned a long time ago that it is very dangerous to make one trade based on the assumption that you will be able to make a 2nd trade with the resulting surpluss.
Besides, you already have Pedroia, who is a solid 2B. So even though Utley would be an improvement, he wouldn't be a huge improvement.
Since you would be making only a modest improvement at 2B, while leaving a huge hole in your starting rotation, I would not make the trade. It wouldn't be a terrible trade if wou went through with it, but It's just not worth the risk. If you had any trouble trading Pedroia for a SP you take a bath on this trade. And even if you did trade Pedroia for a Webb or a Haren, all you did was basically put yourself back in the same position you started.