How to install iPhone/iTouch SPIRIT JailBreak/Questions.?

Ok so i found a website that has the spirit jailbreak.
Im still a little wary though.
I have a few questions...
How do i install it once i download the program?
And if i dont want the jailbreak any more, how do i remove it?
Also, how do i get new themes and such once i have jailbroken it?
Please answer my questions,
Link to SPirit JB is :
http://www.spiritjb.com/

 

1. http://www.youtube.com/watch?v=8Aqcv7UpQ7g

2. Restore via iTunes if you want to remove any trace of jailbreak.

3. http://www.youtube.com/watch?v=ZvDeaigArMk

 

Easy Spirit Jailbreak:
(OPTIONAL: You should restore your firmware to factory default before doing this. iTunes>Restore.)
Update iTunes to 9 at least and your iPod Touch/iPhone firmware to 3.1.2/3.1.3 or iPad to 3.2.
Download the Spirit jailbreak for your specific device and machine. (Mac or Windows, not sure if there are different iDevice versions)
(*MAC USERS: Skip this part)
*Right Click>Properties>Compatibility (Windows 98/ME) Run as Administrator
Start up the program, plug in your iDevice, and click JAILBREAK. Your iDevice should reboot, with a new program called Cydia. You can now download tons of crap, whatever ou want, but you need to add repositories first.
(If you have it fully jailbroken Cydia, you can save the SHSH blobs like so.)