What does inverted triangle in this schematic mean?
I'm just getting started myself, but I think the inverted triangle (the one at the bottom?) is Signal Ground (not power ground). But what you connect this to I'm not sure. I've read about using a metal cold water pipe in your building, or a long metal rod driven into the actual ground.
I'm not sure about the rest, sorry. However, be careful not to overheat the diodes. Apparently it's a good idea to use alligator clips or the like as a heatsink to protect them when you solder.
Good luck!