[quote name='govegan']If you do in-store pickup, is it possible to use a GGC or not, since you'd have already paid for the item in full?[/quote]
BB.com orders for in-store pickup are invalid for the following:
1) GGC combinations, as well as other coupons, except for McD's BB Bucks, which had to be used on the order at time of order.
2) Use of the Reward Zone card for points. (Supposedly fixed in the future)
If you return the item and try to get them to use the BB.com price for the B&M purchase, it wouldn't work. If the website price is different versus the B&M price, they don't change it to match the website, unless you get a nice or dumb customer service rep.