We had a 2003 Hyundai Elantra 4-door GLS sedan in today for a deck and rear speakers and I had just a couple things I thought I might point out to you all just in case you happen to work on one sometime.
The dash trim removal is cake, just get the two screws above the dash gauges, and the two screws behind the ashtray. But make sure you're VERY careful when removing the dash trim--you have to gradually work your way around it before trying to yank the whole thing out really hard. Since it's all one piece, you have to be especially careful of popping out the center area first. If you try to pop out the left side where the light switch is, or the bottom right part where the ashtray is, before getting that center section free, you will more than likely crack the dash trim.
Once I got the trim out of the way and removed the factory radio/pocket assembly, I first tried using a kit, I think the Metra 99-7313. Unfortuately the mounting holes wouldn't line up correctly, and also the kit's pocket is too deep and will hit the metal beam behind the dash. Maybe the 99-7314 would work better but we don't stock those.
I ended up just ISO mounting the deck (Pioneer 4500mp). Here's how I did it:
You leave all 4 screws a lil loose (factory bracket only has 1 on each side of the deck, and 1 on each side of the factory pocket). You want them tight enough that you can hold the whole assembly with one hand by just the pocket, but loose enough so that once it's all in place in the dash, the mounting screws for the entire assembly will be able to pivot the pocket into the correct orientation. The radio sticks out about 1/8" (in relation to the front of the pocket) but you can barely even tell once you have the face on there. Only problem with this is that on most decks you won't be able to fit the trim ring on there, but I still thought it looked pretty good.
The other problem that you'll find when trying to use a kit is that the factory pocket has a kind of slope to it, and it looked a lot better having it in there and matching up with the trim below it than the mismatched aftermarket pocket. Kinda hard to understand until you see it with your own eyes.
The rear deck was a pain in the butt to take apart. Let me save you the trouble by telling you right away that YOU CAN'T FIT AFTERMARKET SPEAKERS IN THE REAR DECK OF THIS VEHICLE!
We were trying to put in a pair of Pioneers and the problem is that the speaker magnet hits the tension rods (I think that's what you'd call them) mounted on the underside of the deck, inside the trunk. After removing the factory 6x9s, the aftermarket speakers will go in but once you try to close the trunk the rods will hit the speaker's magnet. If the speakers are screwed down and you try this, the trunk won't close. If the speakers are just sitting in the holes, waiting to be screwed down, they will pop right out. I guess the factory speakers are shallow enough to avoid these problems. Like I said we were putting in a pair of pioneers so you'll probably have this problem with most other speakers out there. Maybe some Kenwood dual-mags might fit but I really don't know for sure.
As always I'm open to suggestions or ideas; and if you've had more success with this vehicle than I did, please share with the rest of us!