Downloading an image in corona is really easy. Check out the example. Check the console to see where the downloaded file is saved. Download the complete source code from here.
To create gradient text in corona, you have to download ‘Corona daily build 612’ which has functions like setFillColor() etc. You create a new gradient object by calling graphics.newGradient(). You can pass (and reuse) the object in calls to text:setTextColor() and rect:setFillColor(). Here is an example.