>> All D-jet components are now expensive, if available at all. The fuel pumps|
>> are the worst. You need to know this, if you plan to buy that car. If you
>> buy it, start watching eBay for spares.
> H'm. How tough is a K-jet transplant?
I have no idea, but my usual observation is that if it was easy/practical someone else would be doing it, given the large number of SLs running around with the old system.
Look at it this way: with D-jet you have the first generation of automotive electronic injection. So you are driving with a system roughly analagous to the first 'solid-state' radios, technology wise. Nothing wrong with that, just something to keep in perspective.
Like I said, the fuel pump is the worst 'consumable' (high failure rate) part, if for no other reason that these older 116s often seem to be parked for one reason or another for a while, and old electric fuel pumps don't take kindly to inactivity.
The other parts I was warning you about (pressure sensor, aux air regulator, trigger points) don't often pooch and there are now some DIY fixes on the Net for the first two. The trigger points often outlast the cars anyway. However, if you can score spare stuff cheap on eVilBay, by all means why not? You can always resell it if/when you get rid of the car.
One thing you should consider doing, if/when you get the car, is renewing the injector seals. Not expensive and a generally good idea. Also check the condition of the inlet fuel hoses to the injectors, and the rest of the soft fuel lines under the hood.
In the meantime, if you want to learn about D-jet, consider spending some quality time here:
It's a site for Porkers, but Porkke and VeeDub owners have the best FI resources on the Net.