Parts you will need: Bulkheads for the holes, PVC fittings, unions and gate valves to be able to remove parts of the overflow/return line for maintanence if ever needed without the need to break apart the setup, pvc pipe/flex PVC, pvc cutters & glue, drill, wrench to tighten bulkheads, baffles for your sump (I prefer getting glass cut to size at my local glass shop vs plexiglass due to strength), tube of 100% silicone, some type out output nozzle on the tank side for the return (people prefer loc-line fittings)and a return pump.
Now, there are a lot of details I didn't go over because there are many different methods and it is up to you to decide which is best for you. Examples..
Overflow: You can go as simple as a PVC elbo pointed upwards with a cap on it and as many holes as you can drilled into the cap to act as a strainer and make sure no fish go in it, or you can buy pre-made strainers that fit into the elbos. You can make a box and silicone it into place around the hole for an overflow box (this is how my tank is).. and many other ways to do it ..
Sump Design is another - The size of your baffles, how many baffles, location of them, is all debatable but best advice is to plan on what you ideally would like to have as far as equipment in the sump (protein skimmer if SW, reactors, heaters, refugium, return pump, etc.) and make your baffles fit to the specs of that equipment and be functional as well.