I really can't comment on what it would be to fix the car. I do know that the a/c evaporator on a W201 is very easy to access and replace, unlike the W124's.
It may or may not be cheaper to sell it and buy another one, but considering the age of most 190E's, you're just as likely to buy another car that needs other things done.
Maintaining a used car is a fact of life. If you enjoy the car and it looks nice, fix it.
2001 E430, Bourdeaux Red, Oyster interior.
1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".