TIP: to increase the chance of someone helping you, and getting the RIGHT info.... Post the MODEL number of the unit... and maybe the year it was made. Someone may have a similar set, made in the same year and while not being the "exact" model may be able to give you some pointers as most of these sets are pretty much the same... Just the case size being bigger or smaller.
To try to answer your question... UNPLUG the unit...
On most sets you first remove the speaker grill(s)... At the bottom of the screen should be approximately 8 -10 +/- screws.... Remove, then screen should lift off.
Before unhooking screen at top, check to be sure NO sensors are attached to screen assembly. If not you'll find out how much fun it is to hold the screen with one hand... while using your other "two" hands to unplug a sensor harness (yep that's three hands 1 to hold the screen (maybe 2!) and two to unplug any sensor wire, etc left connected IF the screen is lifted up off the upper mounts before any such harness are disconnected.:-)
Lots of fun... and those screens aren't cheap so you don't want to scratch /damage it while taking it off.
If it was me, I'd locate a SERVICE MANUAL for the set...