Going from an iPhone 3GS to a hand-me-down iPhone 4 - Is it basically a matter of cutting & switching the SIM?

I've had a 3GS for going on three years, but my friend just upgraded to an iPhone 5 and handed down his iPhone 4 to me so I wouldn't be that far behind. I know I'll need to cut down my SIM to a MicroSIM form factor with a special tool, so I can pop it in the iPhone 4, but is that basically all there is to it (in addition to all the restoring/resyncing stuff I'll need to do with iTunes)? Or is there a need to deal with our wireless carrier (we're both AT&T) either to apprise them of the switch in hardware or for required technical assistance in the process?