Hi,
I dont know if the layout of the RCD is the same as the RNS, however, if it is, then it should be a piece of cake to remove teh front panel to replace the LCD.
with the unit facing towards you on the bench (screen toward you), on the sides of the unit you should see four torx screws, and i very much doubt its a T7 by the way, i found the RNS used a mix of T10 and T8 torx bits, both should be available quite commonly.
remove the four torx screws on the right and left of the unit and the front fascia should then be able to be removed from the main body of the unit, be very careful and move it forward slowly as there are two ribbon cables that need to be detached, one for the front panel and one for the SD card reader.
the way to remove this is to use a thin plastic 'implement', i found a 'disposable knife' (like the ones you get in picnic hampers/with your sandwiches) works best to gently pry out the 'tabs' either side of the ribbon and then the cable should slide out. do not force anything!
once thats off, it should be straightforward to open up the front panel and swap out the LCD.
good luck!