Will I really have immunity from Prosecution?

three guys I know broke into a home and stole alot of stuff. I bought a couple of the items knowing them to be stolen. I was charged with recieving stolen property. My attorney wants me to take immunity and testify and give all knowledge I know about the crime. Is this a trick or is this really legal. The police want me to take a polygraph and pay restitution for the items I had. I just don't want this to come back and bit me in the . Can you guys give me information please.