We've collected some useful design information:
Minimum bend radius chart for aluminum
Minimum flange widths for press brake forming
McMaster Carr is our go-to place for every sort of fastener, tool, standard and oddball material. If you're new to mechanical design, honestly one of the most productive things you can do is find a McMaster catalog and read it cover to cover. (You can do that on their web site as well.) It's an education in what exists in the world at large to build and run a prototype shop or a factory - what exists to solve every sort of problem in industry.
If you're in western WA, you may find the Seattle Metalheads email group (with web archive) to be a helpful place to ask questions and make connections.