When it comes to drilling the holes, do yourself a favor and get a set of step drills. Harbor Freight has inexpensive titanium nitride coated sets that work great. These are essentially double flute cutters more than drill bits and go through sheetmetal like you can't believe until you use them. They cut clean holes and don't chip on the edges like conventional drill bits.
Just drill a pilot hole with a regular drill bit then switch to the step drill, go slow and keep going until you reach the size you want. It also saves a lot of time and effort changing bits. I've been using my set for over a year on metal up to 1/8" thick and they still work great.
