Yes jailbreaking does void your warranty. But you always have the ability to restore. I would say jailbreaking is completely worth it, but that is just my opinion. You can pretty much find anything you need on the Cydia store. Now if you restore after being jailbroken, there is a slight possibility Apple may know if you've jailbroken before, but there are slim chances. The chances of Apple finding you've jailbroken in the past are very slim unless they feel the need to look through your actual files and all. Apple stores tend not to do this normally, so if you have a local Apple store, I don't think you'll need to worry.

jailbreaking is an AMAZING this, it makes the device how apple should have made it, bu it voids your warrenty and if anything hapens to it, apple wont fix it