Shouldnt be too hard to hop up there, you're probably just over thinking things.
When I trained, I had two different trainers. The first one required I stay up top, which was difficult to learn how to sleep when in motion. He failed to mention the net /restraints and one evening he made a really hard stop and done fell down and knocked the truck out of gear. Interesting way to wake up. Another thing that sucked was the lack of windows up top. The truck was not equipped with an APU, so during the winter, he had this little lunchbox oven and as we all know, heat rises. Felt like it was a hundred degrees up there. 2nd trainer let me sleep on the bottom- I had a sleeping bag. He recognized the value of having a well rested co-driver.