Complete Disk Wipe, reformat and OS change

If your hardware is not too exotic ALL hardware drivers will be included. It is best to test Ubuntu from a live disc (instructions on how to make a live CD/DVD or Live USB can be found here) to make sure everything works. When installing you can simply select "erase everything and install ubuntu" and the disc will be formatted before installing, however formatting using other methods first should not affect installation

The BIOS is on a chip on your motherboard. Wiping the hard drive will have no effect on the BIOS. For additional information have a look this guide on my website for details and a video on accessing and using BIOS. (if it helps let me know so I can post the details here)

With only 512mb Ram you would be best off using Lubuntu 12.04 since it is less hardware hungry.

You don't need to worry at all. Just read all the Installation Instructions carefully, and you'll be all right. However, there are several problems that people encounter mostly because they don't follow the instructions correctly. If you encounter any problem, search the web. Most of the problems are already answered.