yeah don't risk it by killing the DS in some way, just take it to best buy and see what they say to you about it. they'll probably let you exchange it, thats what you paid money for.
When I got a creative jukebox mp3 player a while ago, I got the replacement plan. After a lil while, its hard drive stopped working. I let it sit for a long time, and then took it back and replaced it with a psp. For all I know, it could have fixed its hard drive in that time somehow, but I knew I'd be fine because it HAD failed, and I knew I deserved a new unit due to "their plan, regardless of if it fixed itself or not. He didn't even check if it worked or not, just made sure all the parts were there and gave me a PSP.
When I got my first original DS, about a year after they came out, like this past january, I got a replacement plan on it at gamestop. When the DS Lite came out, my girlfriend bought me a DS Lite, and I gave her my old phatty DS. Then, after a lil while so we'd be sure they had DS Lites in stock, I took it back and argued that DS Download play didn't always work as it should. Lo and behold, the guy at the first gamestop we went to couldnt get their download play or his mario kart to register with my DS, even though I never really had a HUGE problem with the download play. He admitted that the DS Phat owners in a group of friends he had were never able to join their little elite DS Lite battles for some reason, so he was ready to exchange it right there. He hadn't any in stock however, but he told us to go to another gamestop and tell them he sent us so they didnt need to go through the test steps again.
We did just that, but when we got to the second, the Phat picked up the download play just fine. He was like really in disbelief, showing me how he was playing brain games with my DS and we thought we might have a problem, but then all a sudden he changed his tone and was like perfectly fine with replacing it with a DS Lite, no extra charge except for a new warranty if I wanted it.
Finally, just two days ago, after having a cracked hinged DS Lite for a while I decided to try my luck at getting an onyx after hopefully being allowed to use my final replacement plan on MY ds lite (not the one that I got from the phatty). Well, I told the guy it had a cracked hinge, was really nice, and just wanted to know if it was good enough for a replacement. He had no problem whatsoever, just took a quick look at the hinge. Then I started to mention that "maybe they fixed the hinge problem with the new ony"....but he actually cut me off and told me I could choose a different color if I wanted. Well, I chose onyx, got another replacement plan and the only problem I'm having right now is that the bottom screen is yellowish like I've heard is a onyx problem, and there is a dead pixel in the bottom right that the pixel fixer doesn't seem to be able to fix. I'm gonna try to return it for a non dead pixel one, but otherwise I'm a happy camper.
One thing that's hard for me to understand is how they make money with this 20 dollar replacement plans that are so easily "taken advantage" of (quotes because you're essentially getting what you paid the replacement plan for). I think that what they do is send the DSes back to nintendo and get a new or refurbished one and then sell it across the country as a refurb. Meanwhile, they make 20 bucks after essentially lending a DS to us for less than a year and in the grand scheme of things, they don't actually "lose" a DS unit in the process ever, and the 20 bucks covers the difference between the selling price of a new lite vs a refurb.