Would it be wise to purchase a 1997 C230 with 135 K miles $5,000

From one schoolteacher to another, let me tell you -- if they're blowing it out for $5k, there's probably a reason. I would stay away from the MB's altogether, especially if you are not automotive-savvy, as the cost for parts alone can be quite pricey. For example, when I was a mechanic, we got a 1991 MB 300 in the shop with a bad alternator at 149k miles. List price on the alternator by itself was $600. This does not include diag time, a new battery, or labor to install, which was quite involved. Total job would have come to around $1100. The vehicle also needed a muffler -- $235 our cost for this part. I'd sooner see you keep the Park Ave, or get something American-made or at least American-produced, like a Toyota, which will serve you much better.

Is it well maintained? If so the answer is yes, but find a good technician 2 service 4 it will cost u a pretty pennies to keep