We need to be easy with this one. The coolant sounds like the MB coolant. See if you can find out what kind of oil has been used and just stick with changing it and the fluid between 3 and 5k miles and change it hot. Stay away from quick change type of oil change businesses - find a good independent mechanic in the area that you can trust.
You should be able to purchase the appropriate brake fluid at your local auto parts store. Just make sure it is whatever the manual says it should be rated for.
You got any records with the car? Do a search on the 104 engine and you will find out pretty much everything that you need to know about this engine. The issues that they present are pretty well known.
I think they are all around pretty good cars but they ain't a W123 (my inner self saying "are you nuts").