Looking at just the question I would say this is a tough call but looking at your roster and the CJ situation I would absolutely "NOT" take this trade!
You have a monsterous WR crew working already so you don't really need a banged up no QB having CJ in your mix and R.Rice will finish the season as one of the top 3 RB's in the league and he is a dominate little RB so.....absolutely keep Rice at all costs and definatelly don't trade him for a banged up RB in MBIII who has a crap load of RB's to steal carries away from him.
Keep Rice and Nicks absolutely!
Rice >>>>> MBIII
your WR corp >>>>>>banged up CJ (who you wouldn't even play)
Standard H2H 12 Team 1 Pt PPR, Start 1QB, 2RB, 2WR, 1 FLEX (RB/WR/TE), 1TE, 1K, 1 DEF