I assume you don't have an owner's manual for the vehicle? Next time, ask me before busting the lens. I bet that cost a pretty penny. If the lens doesn't have and screws on the outside, then there has to be a way to access the bulbs from the inside. I bet those plastic bulb-holders just popped out from the inside.
Another option would be to look up the make and model of your vehicle on the Internet and see if there is an on-line manual for it or if others have asked and received answers for what you need to do. Google has answers for nearly everything. I guess you already found out that the first thing to check would be the fuse. If the fuse keeps popping, then you likely have a ground or short in the wiring. That might be hard to find.
I think that the ground or short issue in on my trailer, so I'll be taking a look at that next.
The wiring on trailers is generally quite simple and easily accessible, so look for obvious signs of corrosion at connection points. Look for where the insulation could have been worn out by rubbing against something. If all else fails, just run new wires to replace the old wiring. Note that the metal frame of the trailer /vehicle is often used as the ground or return wire.