What happens when you unjail break a iPhone?

I had my iphone 5 jail broken by my friend (he and his sister has theirs jail broken). I did it so I can get free apps. But now my weather app doesn't open up (I don't know if the jail breaking has to do with it but) and I also know that if you need service for your phone the company won't fix it because its been jail broken. My phone is with sprint. If I unjail break it will i be able to get service from the company and other stuff? My friend said he'll be able to unjail break it but it will take a while to do it. I'm wondering if my settings and and everything will go back to normal and the company won't know I jail broke it.

Once you unjailbreak it then all of your data and info is gone, unless you made a backup before you jailbroke it