Not simple in that it's easy to crack an end of the whole pushbutton assy. If I were you, pull the wood (2 screws on lower edge; then pull out and away from the bottom) and remove the 4 screws holding the pushbutton assy in place. That done, try to wiggle it outward. If it comes, proceed. If not, somebody else chime in (I cracked my 300TE assy. but the 500E's came out easy).
You'll see 2 pieces of silver tape covering the bulb holes. While you're here, do both. remove the bulb by a
glue a toothpick to it; b
use some sort of tiny clamp to remove it. Insert the new bulbs with great care, as you don't want to drop them into the assembly to rattle round. I used a medical clamp to do all this (Kelly's clamp).
Glue the tape back in place & reassemble.
Best of luck!
Best regards, Michael