You can run iOS 5 on an original iPad. You need to update your iOS version first and then see what Apps are available for it. You can't do an update unless your device is connected to iTunes on a Mac/PC since older versions of iOS don't support over-the-air updates.
Original iPad, 1st generation can't update past iOS 5.1.1. You will have to download iTunes 11 and backup and restore your iPad in order to update from 3.2 to 5.1.1 I do Apple Tech Support so that's how I know.