The little speaker for those sounds is soldered onto the instrument cluster PCB. I would go for reseating the 2 multi plugs on the back of the cluster first. Then if that doesn't work i would remove the cluster and re-solder the 2 joints where the speaker fits onto the cluster PCB.
Do a search for info on removing the cluster/reseating the plugs, it's very easy and there are pics/guids.