There are just a couple of codes that a tuner can throw that don't mean too much. The rest should still be good. The reason to remove it is just to see if it is tuner related, not the code problem but it may turn something up there.

As for the install/removal of the tuner, I don't have one but as far as I knew it was just a matter of plugging it up and cycling through the menu and restoring it to the stock tune. Look in the owners manual. If you don't have it go online and get it. It should be a everyday guy process for any user. Even a bubba could do it.

What Alan said if it has been flashed and you don't have the unit.