I wouldn't make the trade! Although it's a really nice trade I would rather start the top 3 WR's you have (And they are TOP) and then I would try and make a trade with Marshall and K.Smith or Marshall and Ward for a bettr RB3 (when Marshall get's his act together)
If you make the trade then you will be starting D.Williams and MBIII and then AJ/Moss/Driver??? I would rather start MBIII and K.Smith and then have an elite WR starting corp in Moss/AJ/S.Smith (unbeatable WR corp).....then if you trade Marshall later when he get's his act together or puts together 1-2 good games and K.Smith or Ward and get a top RB2 or RB3 then you will be set!
Nice team BTW......good luck!
Standard H2H 12 Team 1 Pt PPR, Start 1QB, 2RB, 2WR, 1 FLEX (RB/WR/TE), 1TE, 1K, 1 DEF