It's completely understandable to be nervous for your first day. I know I was.
Just be a sponge on Day 1. Ask a bunch of questions, take mental notes on where commercial customers receive, and learn as much about the Diad as you can.
When you are out driving on your own, the best piece of information I can give you is this:
"One package at a time. It will all come off."
As long as they see a day to day improvement, you'll be fine. It's not for everyone that's for sure. However, there is a learning curve, as with every job, and everyone picks it up at different rates. You'll get there if you are willing to work hard.
Oh and be safe.... Your bones will appreciate it as you get older.