Changing car ... probably to a RAV4

Is there anything I need to watch for ? .. is the dash actually a double din or is it a funny size ?

Also i'm going to seriously downsize the installation and run the empeg through a Head Unit, as there will no longer be space for the amp and subs. Is there any problem with this ?

Does anyone know whether Traffic Announements would work over an auxillery input ?

Any advice appreciated .. the units will be professionally installed, but I like to be prepared.

Thanks

Dave