I'm doing a similar hack, the RGB's goodies are going behind my little bit of Lisa and a spare 1400c/G3 is going into the RGB's plastics. The LCD is pretty much spot-on for size and I'll be vacuum forming a clear Plexi bubble for the front over the existing CRT face instead of messing around with flattening the opening. Gotta build a real vacuum forming machine this time, I did some down and dirty 9" LCD Bubbles with mixed, but very encouraging results with a jury rigged setup a while back.

For another great approach: I don't remember the thread, but someone did an absolutely beautiful job of creating a black plastic surround for an LCD behind a Compact Mac's curved bezel opening. Maybe someone remembers the thread, dunno if it was in Compact Macs of Hacks, but it is really worth searching out!