I have wrangled an invite for the duck opener for the first time ever, and need some advice on gear. We will be hunting a low pond/ marsh decoy situation. Not concerned about clothes, was told rubber boots would be fine, not to worry about waders.

Really more concerned about choke and shells:
I have a Remington 870, 12 gauge 3", need to choose the right choke - have modified, extra full and rifled available. If I need another (assuming modified is best of what I have) which?

Shells - I know they have to be steel or something non lead - please recommend what size shot and brand - something I can find easily at Wal Mart, or more likely Gander Mountain. A trip to Bass Pro is possible but unlikely.

I will probably only go 1-2 times this year, and something in the $20-$30 range sounds reasonable and 1 box seems like it should be plenty.

Thanks in advance for the help - hoping to have a great time trying something new this year!