Hi Marcia,
To answer your question, drain both the low water drain lines. An empty line can't burst.
Lots of people here are more qualified than I am, and I also own a 2013 177.
It takes me a gallon and a half to run all the lines properly, could probably do it with a gallon if I was really professional, and it only takes me 10 minutes.
You can crawl under the driver side wheel, in back of it, and drain both those low water drain lines. I'd sure do that if I were you. It's easy.
I question the quality of this dealer.
This web site should start a "Name that dealer" link for experiences just like this.
Maybe the dealer blew it all out with air, added the pink stuff for the pump and drains. But the low water drains don't blow out unless they are open, and still might have pure water and freeze and burst.
Good luck!