Criminal Situation...help!

My friend was arrested and is being held in a county detention center on invalid charges that he was smuggling guns and drugs across to Mexico. Their only "proof" was that 2 other people conspired against him and testified against him. He, at the recommendation of his public defender, plead guilty and offered information that helped in other cases and was to recieve a "rule 35" shortening of his sentence. He is now being pushed to sign these plead papers and does not trust his attorney.He was also suppose to recieve a 5K1, also shortening his time. He has not gotten any confirmation concerning this other than an email several months old from the prosecutor. Should he sign the papers before his appeal time ends? How long does he have to appeal? How do you hold the prosecutor accountable to their promise? He is leary of them keeping thier word before he signs papers? Help!