I've taken my Diesel SL on many road trips - three times to NC from CA, once to AR from CA and once to BC from CA. The car is essentially a 123 with 107 skins.
My road issues have been a failed voltage regulator, two flat tires within 150 miles of each other (improper valve stem installation) and a wheel bearing.
There are several threads about tool/spare parts kits to take with good info. Definitely take fuel filters, return line hose, belts, etc.
A good tip is to only stop at name brand truck stops for fuel. I've got about 75k miles on my current fuel filters as I'm meticulous about where I fuel up. Bad fuel can strand you.
The nice thing about these cars is that they generally fail gracefully. While things like timing chains, vacuum pumps, oil cooler hoses and the like can be catastrophic, most things will provide ample warning and allow you to "limp home" to a place you can get a part/repair.
Look at getting an upgrade to your AAA for the trip. Tows can get expensive quickly, especially out west.
Good luck...pictures are always nice.
Here are links to my road trip threads -
SL Diesel Road Trip
380SL Diesel Coast To Coast Road Trip
Diesel SL - Time for another Road Trip
SL Diesel - Another Coast to Coast Road Trip