The last line in the code you provided wont compile.
the lcd.print() function expects a char, byte, int, long or string (taken from the LiquidCrystal docs) and you're trying to combine a string and an int which the compiler isn't going to understand.
The easiest way to print both would be to have two print statements:
lcd.print("launch in ");
lcd.print(millis()/1000);
Most of this is taken from quickly googling displaying time on an lcd screen. Check out this forum post, it seems similar to what you want to do: click me!