Let me ask you this... What is the purpose of the car? Is this a daily driver? Have you had it for a while or did you just get it? Has it been stored? How long?
How important to you is it that this car get fixed? If it's going to be a perpetual headache, is it in your best interest to get rid of it and get something else?
My thought process here is that you likely do not have the tools and resources to complete diagnostic maintenance. In order for us to help you, we will need eyes, and ears, and hands, to do all of the [things] necessary to determine what is wrong with your car.
What you need is a mechanic. A family friend, or somebody with enough time and tools to do the basics and help determine what needs to be done by a shop.
All of that aside, if you car was my car, I would already have that engine out and sitting on stand.
That should give you some idea of what you have to look forward to.
For a hobbyist... Not a big deal. If you have never been a mechanic of some sort, this is probably not your project.
Trans has to come out to replace seal
Good time for a new clutch if required
Replace and combination of hoses, pump/reservoir, or steering rack
Master cylinder, or lines, or caliper
I'm told the oil and coolant are mixing
This is most likely a head gasket
I'm going to doctor up your thread title a little bit. Maybe somebody here knows a good mechanic in your area that can give you the straight scoop.