Maybe this is wrong to suggest this on an MB forum, but how about a VW Phaeton? You can get low mileage ones for much less than $30k now. They would be great for long highway drives. They are more of a Bentley than a VW. Here's one for $24k in saint louis. I've seen many under $20k already. They are probably on the same level as MB's with repairs. They look like a bloated Passat, though. They do have a real-wood dash like MB's too, they were about 80k new and were built to the Chairman of VW's specs, for instance it can be driven all day at 190mph, with an exterior temp of 122 degrees, and have an interior temp of 72 degrees.
You can even get one with a w12 engine, which should be useful for I-44.
This one is 24k for 44k miles, you can get one for much less though.
http://stlouis.craigslist.org/cto/846868041.html