craigmcd,
Be aware that the high mount brake light gasket is known to leak water into the tailgate light area. I think it was my 2012 that had that issue, an easy fix to replace the gasket with automotive dumdum.
You really don't need to pull the entire headliner down to check those drain tubes. Pull the sun visors, overhead assist handles and the A, B and C pillars (you'll need a Torx 55 bit for the front seat upper seat belt anchor points), and you'll need to pull down the door weather seals to about half way. Then, keeping your hands clean, you can pull the sides of the headliner down far enough to see your drain tubes front and rear, and make any repairs needed. The entire headliner doesn't need to come out.