I'm going a little extra helpful and add the following
1. Jailbreaking is a 2/10 2 being very easy. Just know what home button and lock button is if needed. And ability to read lol.
2. Advantages of Cydia - theming (making it look like various android devices with dreamboard, windows7 phone, sonypsp, nokia, etc) / productivity from tweaks / bluetooth sharing files / notification tweaks like call from notification center & etc. / ability to sms anywhere and whenever* / torrent / action menu (not just cut copy etc) / download from safari / expand your wifi with wifi booster in signals (get technical)
3. Disadvantages - some tweaks are not updated to be compatible but majority are and well this isn't a disadvantage but everything is organized.
With apple signing for updates or restore to current version is very limited on flexibility because they want to prevent jailbreaking.
4.You can unjailbreak your ipad, just uninstall everything that you installed from cydia. Cydia can be kept there . Or you can do a complete restore after a backup and you'll have no cydia just original unjailbroken device. (but if apple updates ios firmware and theres no jailbreak you're out of luck once you get on the next firmware unless with tiny umbrella application)
5. different softwares for jailbreaking provide difference things for developers. but just stick with recommended software for your operating system and your device and you would have no trouble =)