Re: Question about sound dampening
i dunno about the mouse pad, if it would fit inside, you could probably glue it in there. it might rub though.
the best thing i've found, and use on all my bikes, is Plasti-dip spray paint. you can get it at Ace. it's the same stuff that comes in a can you dip tool handles into. just spray it on thick inside the cover, let it dry, and it cuts down most of the noise.
as for the gasket, i reuse mine. i've had the cover off 50 times and i'm still on the same gasket. it actually doesn't really do anything important anyway. there's no fluids inside and if the cover's tight it's not gonna get saturated with water, so it's pretty much useless. i mean, if you were swamp-doggin' it through 3 foot puddles it might be a good idea to have it, but otherwise...
(edit) i'm not recommending you run it without a gasket, i'm just sayin..