How do I get (temperature,DEC) and (pressure,DEC) to work on the LCD?
The Serial.print(temperature, DEC); function is converting the value in the temperature variable to a string, with a base 10 representation of the value, then sending that string to the serial port.
You need to do the same thing, except send the resulting string to the LCD, using LcdString().
Look at the sprintf function. It converts numbers to strings.