Whoa holy cloudy water batman

[TheReefGeek]

You can drill the tank and add the sump later easily, you just cap the bulkheads. Definately go with a drilled tank if you can.

I would also get the tank drilled for a closed loop, do some searches on closed loops.

You don't need the sump to cycle the tank. But yes, you can run the sump without a skimmer for a while.

When planning your sump, dont put too much flow through it, use the closed loop for the majority of your water flow.