Considering a 1LT is basically from $22k upward, YES, that is a great price and right now is as low as you'll see anything GM go, until things pick back up. The incentives are just crazy, for all intensive purposes.
Given how much of a chunk off the price that is, I'd go for it exactly as is and worry about wheels later. Yes, technically the chrome 1LT wheels have a plastic face, but they've turned out to be durable for all the years GM has been using such design and the style/chrome looks fantastic on the car. If you still don't like them, just look for a set of 2LT, etc. wheels after the fact on your own, again for not much. Also to remember, doing a swap of 17" wheels would keep the same tires and not need any other changes, but something like a set of stock 18's would require a computer reflash to compensate for the extra 1" in diameter in all of the car's systems, since the sidewall height is not narrowed with larger wheels--the wheel/tire combos just are bigger overall on 18" equipped models. Ebay can be your friend in this case, frequently...but then again, it may not hurt to ask if they could/would, maybe if there was an extra set around. Just don't demand it.
Hope you can deal soon, and have that new car
For the price, also, no reason to bother with an LS given the extra chrome bits, steering wheel controls, etc. of a 1LT in comparison--you'll be happier in the end, especially if it allows you to get colors you really want.