If you've tried the rice thing and it's still not working, you probably won't have much luck with other tricks. Freezing most likely can't hurt at this point, but I've never had it make any difference. YMMV. You could also try a silica desiccant like the packets in shoeboxes, electronics stores sell bags of it.
You probably won't get a free replacement at the Apple store unless the tech you talk to likes you AND isn't too afraid of his boss. They've been phasing that policy out for a while, and my understanding is that it's really only authorized for major customer service issues these days. They will probably replace it for you for less than the cost of a new iPod, but it will be from replacement stock, not new in a retail box with accessories.
You could also look for a third party repair place, but repairing major water damage is going to approach the cost of a new device, if not exceed it. Most places won't bother.
