I just spent the last four and a half hours, helping my mate build a metal hinged lid for my trailer, by the week-end, I should have it all finished, I have to put my tin sides on yet.
If you are thinking of getting a trailer I would strongly recommend a braked trailer, I also added drop legs to the rear of mine, stops it tilting upwards when you have more weight on the tail end or if your climbing onto it.
Spend a few hours in a car park and learn to reverse it, this will let you get the hang of reversing, but skill only comes with time.