Blender Render VS Cycles?

Hello, I’m new to Blender.

I’m wondering about the essential differences between the regular Blender Render and Cycles. I realize that Cycles seems to be able to do a bunch of stuff Blender Render can’t, but is there an ideal use for each? If I had a nearly completed scene that I suddenly decided I wanted to render with Cycles, is there anything I would need to change about the scene?

(I’m assuming there is, because when I changed my settings to Cycles and tried render view it rendered as a black screen)

Another side-question: Is it even possible to render a glass-like or transparent object in Blender Render? I’m having issues.

is there anything I would need to change about the scene?
Materials is blender render and cycles are not compatible with each other so you’ll have to remake them all. You will also need to update your lighting

Another side-question: Is it even possible to render a glass-like or transparent object in Blender Render? I’m having issues.
Yes.
You’ll have to enable raytrace transparency and adjust the transparency settings. http://wiki.blender.org/index.php/Doc:2.6/Manual/Materials/Properties/Transparency

Read the manual http://wiki.blender.org/index.php/Doc:2.6/Manual