I have an existing cust. with a T1 for outgoing and DID(Norstar MICS 4.1). They want to upgrade the existing T to PRI. I understand that I have to purchase 'PRI enabler' and install the keycodes.
Can someone send me instructions on what I need to program in the Norstar after I input the keycodes? Also, does this have to be cut in conjunction with the carrier and how much downtime on the circuit?

It's not that big of a deal, you just enter the keycodes in programming under "Software Keys", then change your card to PRI under "Hardware". You will need to know line coding info and protocol type from the telco. As for the down time the customer experiences, depends on how quickly you get this done and telco. If my memory serves me right, you also have to go to lines 1-23 and configure for E&M Winkstart.

You should upgrade to 6.1mr also. Some issues with PRI on 4.1. Also change dial route from pool a to pri. Did will be target lines.

Is it necessary to upgrade to 6.1?
What are the issues? Appreciatte your input.

There are issues with 5.0, not so sure about 4.1 at least I don't seem to remember any.