Anyone knows what's the speaker size for our 380 front left/right door? My speaker is pretty screwed and i would like to replace it.

Oh, is it difficult to remove the door trim? do we need any special tools to do it?

you don't need any special tools to remove the interior door panel, however, be aware that the stereo does not produce much power so if your intending on replacing the dodgy speaker with anything decent it wont play.

There have been a few people here who have upgraded their full systems (ie head units, speakers, sub, etc) to very good results. So there are plenty of threads and posts about all that, if you spend some time searching. There was also a very recent thread about taking the door skins off (for fixing broken window winder motor, I think).
I think the front speakers are 5". I'm sure, to a seasoned audio expert, they're gutless... but they sound quite good to me, though I'm not a doof-doof lover or fan of big bass and massive subs, etc.

I will try removing the door trim first before buying a new pair of speakers, in case i can't removed the trim or get the wrong speaker size.

front speakers are 6 1/2 inch, straight swap over for splits - replacing the tweeters is a little trickier though if you use the same spot....bt if your just replacing the driver, no need to worry

if you go aftermarket speakers, they will play, but you certainly wont get thier best performance

the headunit themselves (the intergrated stackers that is, i know nothin about the doubledin type) seem pretty reasonable for a factory unit, i have a Rockford Fosgate 360.1 (An Interactive Signal Processor) connected to my headunit and i didnt need to adjust the gains on that much before it clipped the signal, so it appears it has a half okay output voltage - nor did it do massive amounts of changes to the frequencies the headunit puts out to obtain a flat frequency response

6 1/2 inch will be it, thanks Ricbec.