if you have access to a canoe or boat of some sort it would help ya a bit, you can put out the dekes with it and pick em up as well as any downed birds, if you do have a boat i would recommend leaving it where it will be when hunting for at least a week so the ducks get used to seeing it there.
oh and yeah the 870 is a great gun shot one for years and never had a prob with it, check your local pawn shops too , sometimes you can find a great deal on a good shotgun.