1992 excel replacing stereo.

I recently bought this car, 1992 excel ls 203,000kms
So im wanting to remove the old stock radio deck and replace it with a new deck. Ive tried getting old deck out but have not had much luck. I have been told you half to go through the glove box, so i have the glove box out, but still no where to go, do i need to remove the whole lower dash to get to the deck?
Please any help would be appreciated.

ok i got the the deck out, now what are the colour codes for a 92 radio, i see,

| - - - | - - | - - |
| - - - |......| - - |

is the type of plug,
black brown green | yellow/red red | grey blue
red brown green | | grey/black blue/black

the only one im really unsure about is the orange, my new head doesnt have an orange cable, is orange antenna power?