Jailbreak my work phone I just got an iPhone from my company. I have to access my work email on this iPhone 4. 
However, I can't use Grooveshark as my music service, since it only works on jailbroken iPhones.

How can I jailbreak my phone so that company's server is unaffected? Or would it possibly even be affected in the first place?

How do I un-jailbrake the phone later, so I can return it to my company later unaltered?
Backup with iTunes to restore later, but just go to http://www.jailbreakme.com from you're iPhone, slide to unlock, and wait