So if you want 8 decimals, all you would do is set
uint public decimals = 8;
Then you do not touch any of the (10**decimals) parts. If you are looking to set 1 ETC = 1000 tokens, and your token has 8 decimals. Then you would need to set the following:
uint256 private priceDiv = 10000000;
Because you want 0.001 Ether to equal 1 token, and the price is calculated in WEI. If you put in 0.001 Ether in the converter here you will see it equals 1000000000000000. So you need to set the price to take your decimal into account:
10000000 * (10^8) = 1000000000000000.
Not sure why this line of code does not have the * (10**decimals) part, I think that is why it is confusing - maybe @Neuron can let us know?
Then for your last question, yes you simply need to amend those numbers as you see fit(of course take into account your total supply!)
Let us know how you get on, thanks!