As for lighting, and you want to upgrade to a reef later, I would start with An IceCap 660 Ballast set-up to run 2 54w t-5's with the SLR reflectors. If you want more light can add a total of 4 bulbs. It will be brighter than a 2 bulb vho set-up and produce less heat.I would go with 2 10000k bulbs. You will get ~2years bulb life out of this set-up. When you go full blown reef put 2 250w hqi pendents and split the t-5's, or put 4 more t-5's in if going with lps or soft corals.
As for skimmers, your main problem with running an external skimmer will be the height of the sump without drilling it. If you can have it drilled an external will work great. I will give you both internal skimmer options as well as external. The Urchin will be undersized for your tank even the Pro model.
Internal
Good- ASM G2
Better Schuran JetSkim150
Best H&S 150-f2001
External
Good-AquaC180
Better Grotech HSA150
Best H&S A150-f2001
Any of the exteraal skimmers can be run in sump or external.The Schuran can also be run external, but pump set-up is a little unique. The Grotech and the H&S A150 are recirc skimmers and will be more efficient than the others.
I would run your overflow into a bag holder with a filter sock, skim it, run it over carbon, and pump it back to tank.
I personally would run an Eheim 1262 pump or your return, If you want a cheaper pump look at a Pentair 4000 model, or Mag Drive 950 or 1200.
I hope this helps a some. You are doing the right things about asking questions first.
Just buy good equipment the first time around, and you will save money in fish loss, and not having to replace your system.
I don't think a closed loop in important on a Fish System, and when you turn to reef, Tunze Streams do great about adding flow to a system.