Here's my dos centavos. YMMV, and others may offer contrary opinion...
It depends if you are trying to replicate the beer exactly, or just get a similar vibe. My understanding of Briess amber is that it includes Pale, Cara 60L, and Munich malts. I'm sure other brands are of a similar nature, but I'm not as sure of the makeup of those. So, yes, it would be a different grain bill, but I'm sure it would make a tasty beer nonetheless.
If I was planning this as an extract with a steep and trying to get as close to the original recipe as possible, my inclination would be to swap the 2-row for a pale/extra light DME/LME and steep the Vienna and crystal, but that's just the way I'd do things (not saying it has to be done my way). I would be inclined to go this way simply because a) the Vienna malt flavor is important to this beer, b) the Munich (though tasty) would lend a different flavor profile (again, assuming that this is the DME you are using), and c) I didn't run any numbers, but my gut is that the amber DME may be too dark for this beer (but I may be off base on this point). Regardless, yes you can use it, and I'm sure it would have a tasty end result, but it might not end up as the same beer.
Also, there are differing thoughts on this, but most conclude that flaked corn in the steep would not be the best option. In my early days I did this once, and the beer had problems (maybe not related to the corn), but I avoided it after that in my extract/steep days. I've done a fair amount of reading on this since then, and most say it will add protein and not much else. I'd likely use dextrose or something in its place. Of course, you could also do a mini-mash of the grains/corns to sidestep this entire point.
That's probably more info than you wanted...