Hello, I'm new to the forum and I've owned 2001 Audi TT Coupe since mid February. I've enjoyed it so much without any major problems thus far. However yesterday the Check Engine Light can on and when I did the testing, it showed

17521 p1113-O2S Sensor Heater Resistance Too High Blank 1 Senor1
17536 p1128-Long term fuel trim multi bank 1 system too lean

So what should I do?
After doing a little research, I came into conclusion that I should replace driver side pre cat Oxygen sensor. Also, I'm wondering if I should be replacing the Mass Airflow Sensor as well. I was thinking I could try to just clean that (I noticed a low MPG recently) to see if that would do any good. Any suggestions would be appreciated. Thank You so much!!

John