Ok, here's what to do...
First I would replace the gaskets on the bulkheads, assuming they are used. Hand tighten, plus one quarter turn with a bulkhead wrench or channel locks.
I would setup a Herbie drain since you have two bulkheads. One will be a full siphon the other an emergency drain. In order to set this up you are going to replace the standpipes in the over flow box. They should look like the link below. The strainer can be purchased online or from most LFS's.
http://gmacreef.com/herbie-overflow-reef-tank-plumbing-method-basics/
Next you're going to need threaded adapters on the threaded side of the bulkhead under the tank. This will be 1" male pipe thread (MPT) x 1" slip (Assuming your bulkheads are slip on the flange side and female pipe thread on the other). You will need thread sealant or Teflon tape to create a leak proof joint (Follow the instructions in the video below). Then a short piece of pipe and a 1" Slip x 1" Slip Union. This will allow you to easily remove the drain pipes under the tank if the situation ever came up where they needed to be removed without hacking up your pipes.
https://m.youtube.com/watch?v=Auyhm7YKQEI
You're going to need a stick of 1" SCH 40 PVC pipe and 4x 45 degree elbows. Maybe 90 degree street elbows if the distance is too far to the sumps filter bag holder. Better to go ahead and buy them now and return them later. You'll also need PVC cement, but do not glue anything until you have dry fitted everything first. Pick up a pair of PVC pipe cutters too. They can be bought very cheap at Harbor Freight. Finally you're going to need a PVC gate valve for the full siphon. I would buy a threaded gate valve and install 1" MPT thread x slip adapters on both sides. Gate valves aren't cheap. No sense in permanently gluing them.
Now, you need to place the sump in the stand and figure out how much pipe and where to put the 45's/90's and the gate valve on the full siphon drain. Just eye ball it and cut your pipe a little long to make finer adjustments/cuts as you start to piece it together. The emergency drain can terminate anywhere in the sump, however, I would avoid terminating in the return section. Make sure it terminates above the water level. Above the water level will provide an audible alert that your full siphon has been compromised and needs attention. The full siphon should terminate no more than 1" below the water level.
Once you have it all together grab a beer and admire your work and post a picture on here for any critiques.
Next is the return. Since we used the two bulkheads for the drain you can just run the return up and over the rim of the tank from the back. First install a 3/4" female pipe thread x 1" slip adapter directly on the pump. Then a piece of pipe to above the water level followed by a 1" slip x 1" MPT adapter. Then install a 1" threaded true union ball valve. This will allow you to easily remove the pump for servicing and also remove the valve for cleaning. From this point you will need to determine if you want to run PVC up to the tank or vinyl tubing. Since we're upsizing the plumbing from 3/4" to 1" I don't see any problem with running vinyl and it will insure there's is no vibration transfered to the tank. If you want to go this route you'll need a 1" MPT x 1" Hose Barb elbow and a stainless steel hose clamp. I suggest an elbow because the 1" vinyl isn't very flexible and the elbow will direct it to the back of the tank. Finally, pick up one of these below and another clamp.
http://www.bulkreefsupply.com/return-jet.html (You may need to drill an 1/8" hole just below the water level to create a siphon break.)
Most of your plumbing parts are available at Ace Hardware, Home Depot or Lowes. The true union ball valve may have to be purchased online. BRS sells them.
Last but not least, I would consider adding another pump and buying a manifold to run other equipment like reactors, UV, etc. But we can jump off that bridge when we get there.
I hope this helps or at least gives you some direction. It may sound like a lot, but I promise it's very simple.
