1. If you have GSM service, you almost certainly have CDMA service - there are very few places you'll have GSM and not CDMA (but the opposite isn't true). Even if you don't have CDMA service where you are, you can probably activate the phone, because you can activate it from the Tracfone website. (I say probably because if you need to update the preferred roaming list (the list in the phone that tells it what carriers to use), you'll need service to do that. And don't do any *228 PRL updates unless you're in an area served by the underlying provider - you might mess up your phone.
2. You can direct the underlying carrier by choosing the right zip code when you activate the phone. Keep in mind that this will also give you an area code for the zip code you pick, which might make your phone long distance for people who call you (calls from the phone include long distance and are single rate on the LG).
I know that you'll get Verizon if you pick a Chicago zip code. 60602 will get you a 312 area code, 60639 will get you a 773 area code. This thread says 46372 (Roselawn IN, home of the Ponderosa Sun Club nudist resort) is Verizon. New York City is also a Verizon area.
FWIW, the LG 3280 is the only Tracfone I had trouble activating, but I was activating it on a Maine U.S. Cellular zip while in Chicago U.S. Cellular coverage. I had to call Tracfone CS and get a bunch of codes to enter to get the phone to work, and they had the wrong instructions for setting up voice mail.