Code P0170 on 1999 Mercedes-Benz CLK320

My check engine light is on and I had the code checked, which the code is P170 - Fuel Trim Malfunction Bank 1. How much does it cost to repair this and what happens if I keep driving?

Asked by for the 1999 Mercedes-Benz CLK320
here are some fuel trim code articles that I wrote for RepairPal to help customers and shops understand what is going on with this often confused code condition
I do Emissions work in CA and have dealt with these issues for years.
http://repairpal.com/OBD-II-Code-P0171-and-P0174
http://repairpal.com/OBD-II-Code-P0172-and-P0175

It would be best to find out more about the code P0170 i.e. are there any other codes, because this code just indicates there is a Fuel Trim Malfunction, usually there are other codes to indicate the fuel system is too lean or too rich.
I have found that the best thing to do with Mercedes Fuel trim issues is:

if it is a lean code check for vacuum leaks and then it there are no vacuum leaks and both banks are very lean, ( i.e. LTFT is above 15%) it is often the Mass Air Flow sensor
if it is a rich code, it is often a Mass Air Flow Sensor as well
BUT only use the exact part number Mass Air Flow Sensor, DO NOT use an after market Mass Air Flow Sensor!
2 answers
tuneup fixed mine. Did the tuneup myself, cost $30 bucks in plugs and 3 hrs of my time,