Ok first off i am going to say that a complete understanding of java is not necessary to be able to make mods for minecraft. I used minecraft as a tool to learn java and it worked quite well. i now have a pretty solid base understanding of how java operates. So if You have questions please ask and the people that understand it a little better should try to help you learn. Now to fix your spawn height problem you need separate generation parameters for each ore, like this:
for(int i = 0; i < 2; i++)
{
int xCoord = X + random.nextInt(16);
int yCoord = random.nextInt(30);
int zCoord = Z + random.nextInt(16);
//vein max size
(new WorldGenMinable(mod_wac.oreWaconium.blockID, 4)).generate(world, random, xCoord, yCoord, zCoord);
}
for(int i = 0; i < 12; i++)
{
int xCoord = X + random.nextInt(16);
int yCoord = random.nextInt(120);
int zCoord = Z + random.nextInt(16);
//vein max size
(new WorldGenMinable(mod_wac.oreEnder.blockID, 10)).generate(world, random, xCoord, yCoord, zCoord);
}
for(int i = 0; i < 45; i++)
{
int xCoord = X + random.nextInt(16);
int yCoord = random.nextInt(48);
int zCoord = Z + random.nextInt(16);
//vein max size
(new WorldGenAqua(mod_wac.oreAqua.blockID, 15)).generate(world, random, xCoord, yCoord, zCoord);
this will allow you to change the spawn features of each ore individually so your sand ore will spawn higher