You should plan to do a complete your own Pre-Delivery Inspection. You can use the link below to download mine, or you can search the internet for another one.
This document will take you about 4 hours to complete (don't rush it) and will ensure you understand all the operations of the trailer as well as having you inspect the trailer. This will help you find all sorts of "gotcha" stuff that might not pop up until later down the road (ie...when your 100's of miles from an RV shop). No matter what the dealer says, their PDI will never cover everything.
Complete this PDI and get dealer to fix all issue before paying for trailer...that way the dealer is very motivated to finish.
https://www.rvwiththetanners.com/pre-delivery-inspection
Once you're at the PDI page, you can click on the menu bar at the top to look at our "Should Have" and "Must Have" list under the "Recommended Gear" section.