Water in coolant can be a product of cavitation or a crack or blown HG or bad oil cooler or even something as simple as a loose bolt on water pump for that matter.
Is your coolant level going down if so I'd recommend a thorough investigation of the issues with compression test, leak down test if possible, This can tell you plenty if you have the capability to do them.
As I've said read read read Willy there is tons of info here especially in FAQ and tech sections. Most of the questions you need to find answers to are in there.
As for leaking oil you say it leaks but not from where and that is not helpful to us to help you. I'm thinking that this truck was ridden hard, put away wet loose and worn out from what I'm hearing and seeing.
FYI this could turn into a HUGE investment on your part in TIME first and foremost and in $$$$ too. I'm hoping it's some simple stuff but sounds more complex as we go along.