* Deal worth about 400 mln euros - sources * Prelios, Apollo and Apax among other suitors - sources * Deal seen as prelude to full takeover of Cerved - sources MILAN, March 6 (Reuters) - Italian credit group Cerved is in advanced talks with U.S. investment firm Centerbridge to clinch the long-awaited sale of its debt collection arm which is valued at about 400 million euros , two sources told Reuters. The unit has also drawn interest from Italian real estate and credit management firm Prelios and other private equity funds including Apollo and Apax, the sources said, speaking on condition of anonymity. Centerbridge is the frontrunner in the discussions and could