To get a program written by someone else on your computer/turtle the easiest way is to use the pastebin program that comes standard on all ComputerCraft stuff. i.e. "pastebin get 3mkeUzby OreQuarry" will download AustinKK's amazing quarry program and save it as "OreQuarry." "3mkeUzby" is the pastebin link to that program.
As for a program to build you a platform, that's actually pretty straight forward if you'd like to code it yourself. The only real trick would be making sure it doesn't run out of materials, but that could be done with a little manual monitoring.
If you want something that's already been written, I'd recommend the
versatile shape builder. It's a little overkill for just a platform, but that's what jumps to mind for me. It includes support for resupply stations, so it would also be very easy to make sure it has the materials it needs.