You can bring the vehicle.xml over. I do this all of the time. I have never brought the whole placeable file over. I go though and copy and paste thing's I need. Bringing the entire placeable file would be worth a try, i've just never done it that way (and will try it next time). Theterrain changes will not come. However try bringing the densityMap_ground.gdm from your oldsave to the new one.
The water noise how loud it is and do you notice it when driving or walking? Driving I didn't really notice anything, walking it sounded like maybe I heard some water but it was very low and can't be sure. For field 34 I just drove a truck all over that field and in the grass all around it and didn't notice anything.