Keep the benz. You could have allot of work done by a mechanic for $15,000 and you may be surprised at how much free time you have at school if you don't go drinking every night....or maybe that is just my school.
Seriously though I am a senior in Civil Engineering and had enough time to design and install a WVO conversion on my 240 last semester as well as other assorted maintenance, despite it being the busiest semester so far.