There are no rear deck factory speakers in Contiques. I suspect, Europe, though. Anyway, 6x8's in all 4 doors. Someone has a nice how-to, but I don't know the link. I'm sure it'll show up in a search. It's really just a matter of finding all the screws to remove the panel. Unclip the switches once you have the panel free. 4 more screws for each speaker and unclip the connector.
As for how they will sound, about 1000x better than stock. Don't worry about an amp at first. Try it with HU only and if it's not anough power, get an amp later. Make sure you bypass the factory amp if you have one (check for a silver box behind glovebox).