Any discussions involving MDC or Hansen should continue. My take is that the bullpen is largely in trouble for this season, with or without Hansen. They can address the pen again next offseason or with guy slike Cox and Edgar Martinez continuing to develop. YOu can find MLB average relief pretty easily.
Adding a guy like Helton could be the last significant move that this team needs to make for the next couple of years in my opinion. Adding Helton (even at 80% of his traditional self) to a lineup that has already secured Manny, Ortiz, drew, Lugo, Varitek, Crisp, WMP, etc., for the next few years adds a tremendous amount of defense and OBP skills in a lineup with tremendous power already. If they don't need to make significant moves for pitching or hitting the next few years, and they can get this deal done with Lowell, Tavarez and MDC or CH then that means that Ellsbury, Bard, Bowden, Buchholz, Masterson and Cox are all safe.
In other words, the Sox would give up two overpriced veterans and one of the picks they got for letting go of Derek Lowe (!). Most teams are aware that the sox have had a winfall of draft picks recently by taking advantage of the system, so I imagine they're getting pressed for more than one of those picks with a lot of these discussions.