I've never owned a GSM smartphone before -- will I be able to do anything with the phone without a SIM? I was hoping to be able to do the initial setup, downloading apps, etc. on my home wifi at least. Is there some way I can buy a cheap prepaid SIM with data service in a store somewhere to use it for a few days until my T-Mo SIM arrives? If so, where's a good place to get one?
Clueless as to your local SIM availability, but you should be able to do everything not related to making non-emergency calls (emergency calls should still work even on a phone w/o card) or mobile data traffic (WiFi works). Some settings regarding the SIM card (enable mobile data traffic etc) I'd think not be available until the phone sees a card... Loading and configuring apps (unless, I imagine, they for some reason need phone or non-WiFi data traffic - haven't stumbled on any such apps myself) is perfectly possible - I've just done much of this process for my aunt.
Once she got here it was just a matter of swapping the card over from her old phone and enabling data traffic - everything else was already loaded and configured.