I have my old sony flip face headunit model number cdx-m630 how can i tell if this will fit in the wrx because i figure i might as well use what i have instead of buy a new one if i can

It should fit as long as it works with an ISO-DIN setup which is what Subaru uses. The stock HU comes out and the new one mounts to the existing brackets. Check the specs on your unit but AFAIK all Sonys and most other current brands work with ISO-DIN.

iso din is that like double pockets or something i belive the way its mounted in y old car is with clips or something will i need screws or a wire harness anything you can tell me would help you always come through in answering my posts man thanks

Use the screws from your current radio to mount the Sony. You will need a wiring harness available at any best buy or circuit city. You should also think about a din pocket of some type as the WRX/Forester radio's are double din openings and the pocket will give you a nice little storage are to put stuff in. It will look like this

http://img.photobucket.com/albums/v509/BryanH69/Picture047.jpg

Check the sticky at the top for a link to the Head Unit FAQ. You will have all the info you need in there.

offset

Is there more information on this install? ;)
http://img.photobucket.com/albums/v509/BryanH69/wc01.jpg

is the wiring harness plug and play because i think they used one in my celica maybe that will work. I have done headunit install before but i dont know how the whole wiring harness thing works because it was already done for me i looked in the sticky and dint see anything any help you guy are giving me alot of good advice thanks

The harness is different in your celica. It will not fit here....you will need to buy a new one.

Which will cost you around $12 at circuit city or something. Just ask them for a 'Subaru wiring harness'....all subarus since like 1993 are the same harness.