I'll explain my issues, can someone identify my problem so I know what itll cost

What is your question?

I bought a 2002 Mercedes s430 off of a guy on Craigslist a couple months ago. I know nothing about cars and there mechanics under the hood and little else wear but I was impressed by the cars smooth drive and everything seemed to be great. A week after having it and letting my boyfriend drive it all week long, the car somehow won't gear shift anymore. It stays in w mode which I think means winter. Which I usually just say that it's stick in second gear when I explain the problem to people, I'm not sure if it's actually the 'second' gear. Anyhow, when this happened the check engine light came on and it's been about two months, I haven't gotten it fixed yet and so obviously the check engine light has never left. When I drive it I try to drive it only on streets, not freeway. Cause I can hear it making noise as if it's over exerting itself when I get to a higher mph and it nears the red zone of my rpms quickly around 50mph our higher. Then a couple of weeks ago I got a malfunction message on my dash telling me to check my coolant. So I bought coolant and before I knew it the dash was telling me to stop the car. So I pulled over had two guys help me. When they put the coolant in they informed me that one of the little hoses that goes into the container that holds all the coolant is broken. It was barely attached on one side and showed me the sprays that you could see inside my hood from that coolant hose. So I still haven't gotten it fixed because for one I know it's gonna be a lotof money since it's Mercedes and because I can't find a proper time to take it in cause I need to make a day that I can actually go without it. Its important ib fix it though. But anyhow last night the coolant message came on my dash again and so when looking under the hood, I noticed that the hose completely broke off. My boyfriend super glued it. Can anyone tell me if all these issues are from one problem or is the gear stuck and engine light and coolant sperate issues. How do I identify what the repair/problem is so that I can do an estimate on this website for the cost of the repair. I don't even know how the problem is identified.