I believe it's always less expensive (in monetary terms) to keep an existing car running than to purchase a new or newer one. On the other hand, less expensive monetarily isn't always the best choice. Old cars tend to require more frequent repairs and the "headache" associated with those repairs has to be considered in the valuation of the car.
The 190E is at a point where repairs will start to cascade. New struts/shocks may reveal the need for new bushings, tie-rods, ball joints, etc. The engine may be sound, but the alternator, water pump, a/c compressor may fail. None of these things, individually are too terrible to fix but if you have to replace half of them in the next two years while trying to depend on this car as a daily driver you're going to be annoyed.
The real question is, "does the 190E still meet your automotive needs?" If it does and you are otherwise happy owning it, then spend the money on maintenance and continue to drive it. If it doesn't meet your needs and you have a buyer, sell it and move on.