Not knowing anything about the condition of your car or where you live, I checked the Kelley Blue Book value of your car using my zip code, mileage at 100,000 miles, and the condition as good. Using this, the private party retail value is $13,850. I've found that Kelley Blue Book is usually high compared to actual market value, so maybe it's worth $12,000.
Given its value, it's worth very little with a blown motor in it.
You certainly have enough value in the car to drop in a new engine, rebuild your existing engine, or buy a reman engine, and still come out on top.
Whatever you do, it's a no-brainer that the car is worth getting the engine taken care of.
2001 E430, Bourdeaux Red, Oyster interior.
1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".