Does it matter what port # I change it to? Does it have to be specific or can I just change like the last number in the sequence and it will work?
Do enough research to be reasonably sure you're not using a port number from any other coin. If you're not sure pick a random one between 10000 and 20000 -- only two coins I'm aware of have used numbers in that range (worldcoin and one other coin I forget the name of), so if you pick it randomly you probably won't pick the same one. Testnet would be that port plus 10000. RPC port is that port plus one.