| * Head gasket likely to fail, if it hasn't already done so. USD1500 job at an indie. Don't even dream of giving the job to a main dealer. Make sure the head is checked and, in all probability, skimmed, or the repair may fail again. The usual failure point is the back of the block on the left-hand side viewing from the front; check for dark oil streaks under the car, as a drip from the failure point may not be obvious. Also check for oil in the coolant. If it does need doing, get at least USD 1000 knocked off the asking price.
* Timing-chain cover may leak.
* Front wings likely to rust; better replaced than repaired. Area beneath tail lights is also vulnerable.
* People do say that the window electrics fail.
* Reliable? Yes.
* Durable? Yes.
An 88 pre-dates the wiring-harness problems that dog the early--mid 1990s cars (and other models). I've had my 1996 E320 Coupé for eight years and do not expect to sell it, such is the satisfaction and enjoyment I get from it.
If you do go for it, get all the fluids changed. 89k over 20 years is the sort of under-use mileage that makes people think they don't need to worry about engine oil, ATF, brake fluid, rear-axle lubricant, etc.
The Mercedes-Benz E-class owner's bible is well worth looking at (Bentley Publishers, 0-8376-0230-0). I'd also get an independent expert to inspect the car. | 
