CoreyDL

The sending unit was in the left rear fender. I did not look to see if their is an access panel there. I know that the whole sending unit had to come out to do the repair though.

Initially they thought they would have to go up through the wheel well liner, but changed their minds.

silverd2

There is a large seal under both covers in the trunk, one of yours apparently leaking...each side has a gas level sensor/sender.

The only thing in the fender well is the leak detection pump, but it does have a sensor integrated to read pressure during it's automatic (or VagCom) tests. This sensor will record a DTC if the system fails it's leak/pressure test. The only things accessible in the trunk are the level sensors.

When the leak detection pump (only accessible from outside, behind the fender liner left/rear) operates shortly after start up, as a regular test, it pressurizes the gas tank and evap system well beyond it's normal pressure...then reads how long it takes to bleed off.
With a bad leak in a seal in trunk, it would not only blow gas fumes through that failed seal, it would be sucking much more air than normal through the inlet (with small air filter on LD pump) in the fender well. When the system is leak-free, you normally won't hear air being drawn in...but, being unable to pressurize the system, because of a leak, you would very likely hear air sucking in, trying to create pressure. "Unproductive" pumps of any kind tend to create abnormal noise of some kind. So, it makes sense you would hear it during a malfunction.