puck and AT commands

Yes, it should be fine. There's an AT command library to make it a little easier: http://www.espruino.com/AT

Something like this should do it:

Serial1.setup(9600, { rx:..., tx:... });
var at = require("AT").connect(Serial1);  
// at.debug();
// Send command that returns multiple items
at.cmd("AT+FOO\r\n", 1000, function cb(d) {
  if (d===undefined) ; // we timed out!
  console.log(d);
  if (still_waiting_for_more_info) return cb;
});

Do you want to use the internet connection from the 3G modem, or just the ability to send text messages?

There's a module for SIM800/900 that'll do full internet connectivity, and that could probably be modified pretty easily for your particular 3G modem as well: http://www.espruino.com/SIM900