I'd be willing to give some clean vocals a shot... but I am terrible with writing lyrics too so I doubt I'd be able to do that.
I've done a quick vocal recording over Scar Symmetry - Dominion... I've had to turn them up pretty loud to be heard over the original.
http://www.silentdescent.com/sneapforum/DominionVocal.mp3
If it's not what you're after, that's fine I'm not going to take offence
If you want me to rerecord the backing track underneath it to remove the original vox I can probs get that organised too.
Tom