I'm planning on purchasing an '04 4wd Tahoe lt with 108k miles, during the test drive the cel came on. The dealer ran the codes and found that an o2 sensor was bad. The dealer is cool and is replacing the sensor with no warranty and honoring the price. I found out today that they are replacing the maf as well. I'm happy that the dealer is taking care of it but am concerned about walking into a lot of problems. Is this common? Is there something else I should be looking for?