You might also take a video camera with you and have someone make a movie of everything that is being done.
Fill all Tanks until you see water in the tank, shower and commode. When you see the water go outside and look all around, then look all around inside. Then drain the gray and black tanks. Then fill your fresh water tank and see if it will fill completely. Remember the sensors in the trailer are not always correct.
I would take a water hose and spray it hard all around the doors and slides then check for leaks.
One thing about a trailer is that water is it's worst ememy.
You should go over all the functions of the trailer. Raise and lower the landing gear. Turn on all A/C's, furnace, Look at the springs, tires and axles. Make sure the U-Bolt nuts on the axles are tight. Mine and many others were loose.
You will not get a good sewer hose. Get a clear 45* adapter and a new sewer hose.
Run the slides in and out and make sure they are not dragging. Check the Refer and make sure it is cooling. Check the front clothes rack bar and make sure it is securely attached. Due to bouncing a some of them will come down.
Living in it atleast one night would be a good deal also.
FWIW
BC