Tad late to this party, but I have seen people turn that same model of sump into a fuge in the past. Should be a pretty easy switch by just replacing the bioballs with a handful of cheato. I didn't see a finished discussion on your lighting, all you need is a simple PC
light for it. If the top of your sump isn't glass, as I believe that it isn't, you can get a simple clip on light at either your hardware store or pet store. It has got hard to find the cheap clip on lights at some hardware stores, which is why I'm mentioning going to the pet store and getting a reptile light. Same light setup they just use a UV
bulb in them. Simple switch out of bulbs if it even comes with one at all.
Though, if you want to get a piece of glass for on top this is also simple. Lowes will cut pieces of glass for you for super cheap. This is where I got the glass for the sump I just made. Then while you are there, you can see if they have a cheap work light! Good luck, I still haven't found one so I'm reusing my old reptile light, just getting another piece of glass as a "top" for it.