you should spend the $ 100 on an inspection. You need to get the car on a lift. You won't feel a leaky transmission or leaky shocks in a drive around town nor will you feel worn flex discs. An exhaust is not cheap either. If you cannot perform maintenance like changing shocks, brake pads, vacuum hoses etc. yourself, this will become an expensive car. I don't know whether your model has the air suspension, which is even more expensive to maintain.
You can spend $1000 easily on the suspension alone if MB services the car. An MB rebuilt transmission is $1700 plus labor to install.
I spent $3000 within 2 months on a car that I thought was perfect when I bought it.
There is a reason why the trade-in is so low.
Don't get me wrong, they are fine cars when maintained, but that comes at a price.