Diesel Bombers - Mickieo

Hi Diesel Bombers. As a new member, I sure could use your advice. I've owned a 1991 Mercedes-Benz (M-B) 4D sedan 300D series with a 3.5L 16 F1 motor. It's got 127K miles on it and has always been babied, never abused. Most everything works really well, except for the cylinders. My mechanic told me last month that 5 out of the 6 are leaking, but that I should be able to get a few more miles out of it. I didn't realize just how few those miles were, however, when I decided to drive it to our local M-B dealership just to see what kind of a trade-in I might get. They couldn't get it started again and I had to tow it home. Obviously, no trade-in was offered. My mechanic, whose worked on it for years, was surprised the engine blew. I can't turn it over; the dear old thing really appears to be shot. So much of the rest of the car is in good condition, just needs engine work.

Here are my questions for any DBers to tackle:

Is this model and year considered a collectible? Would there be potential new owners who would want to restore it to its original glory, at least engine-wise?

Is it worth having a new engine installed? I was told that my car has the 300 series aluminum engines which haven't stood the test of time. I'm not personally interested in restoring the car, but I know I can't get much for it as it is now.

If I decide to fix this car, would I have to reinstall an aluminum engine or could the car take something w a better track record?

Could I get my money out of a rebuild? As it is now, the car won't bring much. I've checked w my accountant and it won't benefit me to donate for a tax credit.

If not rebuilding, where's a good place to market it as is? Parts dealers don't want to give me much at all.

Any feedback will be greatly appreciated. Thanks, guys!